Oboe, the gondolas were a field modification on the 109F. With the G, the wings were pre-wired and bracketed for the gondolas. Hence, why we have them for the G bit not the F. The G-6 were also equipped with the mounts for the WGr 21. So, while these began life as field mods, they became factory options. As far as I know, the Malcolm hood was never installed during P-51 production.
I believe the .50 cal gondolas on the P-39Q are like the 109G in this respect.