Oh god... good luck. The crank from the old image .12 engine will fit in an ae .15 and run (i have set a few of them up that way). The location of the flywheel and clutch requires the use of the original traxxas engine or crank if you want the same engine location. You can always drill some new motor mount locations so a regular style engine can be fit. I occasionally see the NOS image .12 engines on ebay... I would wait for one of those to come along before messing the thing up. Not the fastest engine, but runs and looks good.