Unfortunately not sure which model the Slapton tank is - but even if it were an M4A4, the engine would be too badly corroded to be of use. Engine wise, I think that Chrysler bolted 5 engines around a central core - suspect these were stock engines as undersand this was done because the Radial Aircraft engine was in short supply. To get the new "multibank" into the tank they had to stretch the chassis a little... hence the Chrysler Shermans are all a little longer than those from other manufacturers.