The Lincoln motors starting with the 52 317and then the 55 341 and 56 368 are the MEL design. I don't not remember my 383 Merc having the combustion chamber in the block, but you could be correct, it's been a long time ago. The MEL block had the same bellhousing bolt pattern later used on the FE starting in 52 and the easiest way in the day to put a 4spd hydromatic on an FE was to get one out a 52-54 Lincoln. (Yes, the Lincolns used the GM 4 spd Hydro back then)