Ok, here's my reasons for using the OM615 in my project and putting the OM616 into the W115...
Aesthetics. Nothing more.
The project is an old hot rod. The OM615 looks like more of a vintage engine, it just has a better look for what I'm doing. I'm not concerned with the power. If I want power, I'll take my '67 Barracuda out for a joyride.
I heard before about the oil filter housing. What if I rigged a remote filter setup? Keep in mind, I'm pretty handy, I don't mind rigging things to work, and I have a god friend with a masters in mechanical engineering who's rarin' to help me on this one. Basically, no matter how hard, even if it involved frame notching, balancing, and machining, we're gonna try to make this happen. I'll try to check on the oil filter housing in the next coupla days.