RE: Easy(ish) Combo for 150mph?
150 with a quickie is easy. Any used (but not used up) Nelson or Jett racing engine on about any quickie will do it, been doing it for over a decade. Nothing to it.
Aim higher, there is going to be a FLOOD of Q40 engines dumped on the used market, buy one and build a Q40 airframe and you can easily go into 180-190 mph region. A 5 mph advantage means the world in racing, but for sport flying just lower the nose on the next pass.
150 on the cheap, go with the quickie, clean it up slightly, and put a Nelson or Jett pipe on a good .45 with a racing prop clipped down slightly.