I'm not in SF but the M104 had at least 2 different oil pans. The front sump was moved a few inches between the two.

Valve covers changed over the years. Heads should be the same for all years except maybe for an EGR tube on early motors in addition to the AIR diverter valve, both are in the same exhaust manifold area.

I'm not sure if various block mounting holes changed. I know that at least back to 95 there were 2 locations for motor mounts.