If you're having trouble finding an engine for your car (any small block with compatible crank, and side exhaust to match your header/pipe, or rear exhaust and new header/pipe) you are likely to struggle finding replacement parts for the car itself. My advice: look for another car. I have two HPI belt drives, an original RS4 with original .12e engine, and a hopped up RS4 2 with an OS .15 CV. Both two speeds and both running great, but parts for these things are rather scarce. I'll soon find myself in the same boat as you, and may even start looking at options for replacement engines later today. I'll post back if/when I find something.