According to D. Platt he suggests a .90 to 1.8 cu in glo 2 cycle for his FW 190. If I want to replace that with a 4 stroke gas engine what might I consider?

If your talking gosoline then i'd go with either one of these two saito engines they are such a good running engine it's increadible. Plus they are so fuel efficient that you could get away with only a ten ounce tank to save a little weight on fuel that it would run for about two hours on that much fuel. The two engines are the saito FG 30 which is yet to be released but is basicly a 1.80 converted to gas & the other one is the FG 36 that is 2.20.