By later 1942 many had their MG 15 swapped to MG 81. The 12/42 manual for H-11/-14/-16 states a MG FF/M in cockpit front, MG 131 in top rear and MG 81Z in bottom rear with MG 81 or 81Z in side mounts.
H-20 changed this to MG 131 in cockpit front, top read and bottom rear, bottom front could hold a MG 81Z and side guns were MG 81Z or MG 131. The top rear MG 131 was in something one could call a powered rotating turret.
Later war He 111 production:
H-11 301
H-11 TO 200
H-14 50
H-16 200
H-16/R1 900
H-20 770