Just about nothing is the same between those two. The intake has air injection holes that make the manifolds different and that's not all. The dist on the 74 has points and trigger points. The 78 has inductive impulse generators and no trigger points. The valves are adjustable on the 74 they are hydraulic on the 78. The fuel injection is D-jet (Druck - air pressure regulated) on the 74 and CIS (Continuous Injection System - hydraulic) on the 78. The differences in fuel system change the manifolds completely.
As it turns out there are larger differences here than any change to the V8 till the 119 motors came out.
Bosch Master, ASE Master, L1
33 years MB technician