Is this what it's stated to be?
 

https://www.ebay.com/itm/Detroit-Die...UAAOSw30tZrYv-

It is undoubtedly a twin 6-71, but some items like the aircleaners and rocker covers are too modern for WW2, but of course, could have been replaced. But features like the clutch levers and hand throttles look like this might be more like a Marine power unit than Sherman?

Ahh, if I keep browsing e-bay, I find this:

https://www.ebay.com/itm/Detroit-Die...MAAOSwA29Y5WcX

A twin 6-71 genset, with clutch levers and instrument panel just like the supposed "Sherman" engine.

Remember that these twin GM 6-71 sets (and even quad sets) were developed for generator / pump / marine, etc. use before they were fitted into Shermans. US policy was strongly that tank engines should be petrol, air cooled, radials for best power to weight ratio and compactness but the needs of maximum production forced them to develop the various other engine arangements. Even then the US standardised on the Ford GAA liquid cooled petrol V8, then reverted to an air cooled V12 Continental petrol engine before developing that into a diesel, purely for better fuel efficiancy. The diesel Shermans went to the UK and Russia and post war to Canada.

If anyone is considering one of these generator / pump power units, they are basicly the same as a tank engine but could be assembled to turn the wrong way (move the timing gears around to change it) and can be of a different power output (camshafts, injectors, govenor settings). Post war developments improved the breathing with different ports in the liners and eventually 4 valve heads (all exhaust valves). That put the HP up and didn't change the look of the engine untill they went to cast aluminium rocker covers from the pressed steel ones. All the parts are easily available but at modern commercial prices.

David

apparently there is also the question of the gear ratio in the unit that couples them together..

Hi the industrial/plant twin sets are geared down to the transfer case out put.
The transfer case is deeper than the 6046 twin set.
The other main thing missing is the fan drive gear case cover this is very hard to get and all the relevant gears as unique to 6046.
The industrial twin set does not run the triple oil pump needed to go up and down steep hills with a flat sump.
If engines are right hand turn will need to be converted to left hand turn some new timing gears will be needed and cam shaft.
The exhaust manifold and water manifold on the head also can not be got from Detroit as unique to the 6046.
6-71 engines are easy to get in uk and us so the most useful bit on the twin set shown is the clutches flywheels and the engine side of the transfer case,still need a lot af unique parts that can not be got from Detroit to make into a 6046.