Here is a .cfg sound file that a p51 that came with FSX. Something like this could be used.
[FLTSIM]
product_code=FSIM
[SOUND_ENGINE]
number_of_engines=1
eng1_combustion=COMBUSTION.1.00
eng1_non_combustion=NON_COMBUSTION.1.00
eng1_prop=PROP.1.00
eng1_starter=starter
eng1_shutdown=shutdown
eng1_combustion_start=combstart
[STARTER]
filename=P51_starter
viewpoint=1
link=starter.1
[STARTER.1]
filename=xP51_starter
viewpoint=2
[COMBSTART]
filename=P51_startup
viewpoint=1
link=combstart.1
[COMBSTART.1]
filename=xP51_startup
viewpoint=2
[SHUTDOWN]
filename=P51_shutdown
viewpoint=1
link=shutdown.1
[SHUTDOWN.1]
filename=xP51_shutdown
viewpoint=2
[COMBUSTION.1.00]
filename=P51_rpm01
flags=0
viewpoint=1
rparams=0.000000,0.749000,0.270000,1.080000
vparams=0.000000,51.299000,0.002000,51.299000,0.003000,50.000000,0.023000,51.200000,0.051000,7.200000,0.088000,0.000000,0.226000,0.000000,0.226000,0.000000
link=COMBUSTION.1.01
ConePitch=0.000000
ConeHeading=0.000000
InsideConeAngle=360
OutsideConeAngle=360
OutsideConeVolume=10000
[COMBUSTION.1.01]
filename=P51_rpm02
flags=0
viewpoint=1
rparams=0.000000,0.595000,0.470000,1.110000
vparams=0.012000,0.000000,0.023000,5.600000,0.051000,52.000000,0.171000,57.600000,0.213000,18.400000,0.259000,0.000000,0.910000,0.000000,0.910000,0.000000
link=COMBUSTION.1.02
ConePitch=0.000000
ConeHeading=0.000000
InsideConeAngle=360
OutsideConeAngle=360
OutsideConeVolume=10000
[COMBUSTION.1.02]
filename=P51_rpm03
flags=0
viewpoint=1
rparams=0.060000,0.500000,0.484000,0.812000
vparams=0.104000,0.000000,0.174000,18.400000,0.215000,58.400000,0.403000,70.400000,0.458000,16.800000,0.572000,0.000000,0.972000,0.000000,1.000000,0.000000
link=COMBUSTION.1.03
ConePitch=0.000000
ConeHeading=0.000000
InsideConeAngle=360
OutsideConeAngle=360
OutsideConeVolume=10000
[COMBUSTION.1.03]
filename=P51_rpm04
flags=0
viewpoint=1
rparams=0.363000,0.776000,1.000000,1.000000
vparams=0.333000,0.000000,0.403000,16.800000,0.447000,72.800000,0.850000,97.600000,0.991000,100.000000,1.000000,100.000000,1.000000,100.000000,1.000000,100.000000
link=COMBUSTION.1.04
ConePitch=0.000000
ConeHeading=0.000000
InsideConeAngle=360
OutsideConeAngle=360
OutsideConeVolume=10000
[COMBUSTION.1.04]
filename=xP51_rpmr01
flags=0
viewpoint=2
rparams=0.000000,0.901000,0.373000,1.189000
vparams=0.000000,40.000000,0.002000,40.000000,0.025000,40.800000,0.056000,4.800000,0.088000,0.000000,0.259000,0.000000,0.345000,0.000000,0.345000,0.000000
link=COMBUSTION.1.05
ConePitch=0.000000
ConeHeading=179.999985
InsideConeAngle=90
OutsideConeAngle=240
OutsideConeVolume=9900
full_scale_distance=90
[COMBUSTION.1.05]
filename=xP51_rpmr02
flags=0
viewpoint=2
rparams=0.000000,0.623000,0.576000,1.012000
vparams=0.010000,0.000000,0.032000,5.600000,0.051000,40.800000,0.197000,47.200000,0.243000,12.000000,0.329000,0.000000,1.000000,0.000000,1.000000,0.000000
link=COMBUSTION.1.06
ConePitch=0.000000
ConeHeading=179.999985
InsideConeAngle=90
OutsideConeAngle=240
OutsideConeVolume=9900
full_scale_distance=90
[COMBUSTION.1.06]
filename=xP51_rpmr03
flags=0
viewpoint=2
rparams=0.000000,0.568000,0.801000,1.320000
vparams=0.174000,0.000000,0.218000,12.000000,0.236000,48.000000,0.484000,60.000000,0.528000,13.600000,0.627000,0.000000,1.000000,0.000000,1.000000,0.000000
link=COMBUSTION.1.07
ConePitch=0.000000
ConeHeading=-179.999985
InsideConeAngle=90
OutsideConeAngle=240
OutsideConeVolume=9900
full_scale_distance=90
[COMBUSTION.1.07]
filename=xP51_rpmr04
flags=0
viewpoint=2
rparams=0.377000,0.724000,1.000000,1.035000
vparams=0.398000,0.000000,0.493000,11.200000,0.521000,60.000000,1.000000,100.000000,1.000000,100.000000,1.000000,100.000000,1.000000,100.000000,1.000000,100.000000
link=COMBUSTION.1.08
ConePitch=0.000000
ConeHeading=-179.999985
InsideConeAngle=90
OutsideConeAngle=240
OutsideConeVolume=9900
full_scale_distance=90
[COMBUSTION.1.08]
filename=eng_damage
flags=2
viewpoint=1
rparams=0.000000,0.940000,1.000000,1.250000
vparams=0.000000,12.800000,0.002000,6.400000,0.002000,6.400000,0.002000,6.400000,0.002000,6.400000,0.002000,6.400000,0.002000,6.400000,0.002000,6.400000
link=COMBUSTION.1.09
ConePitch=0.000000
ConeHeading=0.000000
InsideConeAngle=360
OutsideConeAngle=360
OutsideConeVolume=10000
[COMBUSTION.1.09]
filename=eng_fire_1
flags=16
viewpoint=1
rparams=0.000000,1.000000,0.000000,1.000000
vparams=0.000000,90.400000,0.002000,89.600000,1.000000,90.400000,1.000000,90.400000,1.000000,90.400000,1.000000,90.400000,1.000000,90.400000,1.000000,90.400000
link=COMBUSTION.1.10
//[WEP]
//filename=P51_wap,xP51_wap
ConePitch=0.000000
ConeHeading=0.000000
InsideConeAngle=360
OutsideConeAngle=360
OutsideConeVolume=10000
[COMBUSTION.1.10]
filename=xeng_damage
flags=2
viewpoint=2
rparams=0.000000,1.000000,0.000000,1.000000
vparams=0.000000,0.000000,0.002000,38.400000,0.002000,38.400000,0.002000,38.400000,0.002000,38.400000,0.002000,38.400000,0.002000,38.400000,0.002000,38.400000
link=COMBUSTION.1.11
ConePitch=0.000000
ConeHeading=0.000000
InsideConeAngle=360
OutsideConeAngle=360
OutsideConeVolume=10000
[NON_COMBUSTION.1.00]
filename=P51_noncombust
flags=0
viewpoint=1
rparams=0.000000,0.590000,0.540000,1.030000
vparams=0.000000,0.000000,0.040000,0.000000,0.299000,0.000000,0.477000,0.000000,0.701000,0.000000,0.740000,0.000000,0.740000,0.000000,0.740000,0.000000
link=NON_COMBUSTION.1.01
ConePitch=0.000000
ConeHeading=0.000000
InsideConeAngle=360
OutsideConeAngle=360
OutsideConeVolume=10000
[NON_COMBUSTION.1.01]
filename=xP51_noncombust
flags=2
viewpoint=1
rparams=0.294000,0.933000,1.000000,1.162000
vparams=0.000000,0.000000,0.266000,0.000000,0.287000,92.800000,0.428000,100.000000,0.998000,100.000000,1.000000,100.000000,1.000000,100.000000,1.000000,100.000000
ConePitch=0.000000
ConeHeading=0.000000
InsideConeAngle=360
OutsideConeAngle=360
OutsideConeVolume=10000
[PROP.1.00]
filename=P51_prop
flags=2
viewpoint=1
rparams=0.000000,0.561000,1.000000,0.645000
vparams=0.000000,0.000000,0.310000,6.400000,0.440000,5.600000,0.606000,6.400000,0.757000,0.000000,0.917000,0.000000,0.998000,0.000000,1.000000,0.000000
link=PROP.1.01
ConePitch=0.000000
ConeHeading=0.000000
InsideConeAngle=360
OutsideConeAngle=360
OutsideConeVolume=10000
[PROP.1.01]
filename=xP51_prop
flags=4
viewpoint=2
rparams=0.000000,1.000000,0.000000,1.000000
vparams=0.000000,0.000000,0.264000,0.000000,0.537000,0.000000,0.731000,11.200000,0.914000,12.000000,0.998000,12.000000,1.000000,10.400000,1.000000,10.400000
ConePitch=0.000000
ConeHeading=0.000000
InsideConeAngle=360
OutsideConeAngle=360
OutsideConeVolume=10000