[Frank Miller]

I think the 8ba block was pretty much the same. There were some minor differences such as valve rotaters and connecting rod design. Mercury used a longer stroke crank but otherwise the heads made the difference. Mercury heads had larger combustion chambers to account for the greater CI and maintain the same compression. 8RT were the truck heads. I believe these were slightly lower compression for more low end torque. EAB were a little higher compression and the combustion chamber had a better flow design. Do a search and you'll find these are the best performing heads and I have heard they're as good as those expensive finned ones.