I just set an O.S. RG-X on my NMT (which had the engine removed already) and I think a stock Savage engine mount and some creativity might allow it to work without specialized engine mounts or flywheels. The RG-X's pullstarter is too large, unfortunately, but a Hyper's pullstarter is quite a bit smaller than the RG-X's so I bet that'd work. I've got an 8-port in my Savage right now, I might pull that out to see if it'd work.
The only thing I can see that's in the way is the brake mechanism hits the carb slide. The carb can be rotated which might take care of it. Otherwise the brake can be moved to the front of the spur gear housing.
Of course driveline strength and overall chassis strength might become issues with such a strong engine, but that's the fun part, right?
I'll look into this some more...