Harley engine swap info needed

Due to illness that prevents kicking over my trike, I find myself in the position of needing to swap out the engine of my 1942 Harley Servi-car. It is the (of course) 45 cu in flathead, kick start, 3 speed manual shift, no reverse. Does anyone have info on what engines will fit without whacking up the frame. I feel bad enough about having to change the engine without modifying anything else. I know there are a few electric start conversions that exist for the flathead, but they're all so expensive, and a bit chancy as far as reliability. I'd appreciate any help out there.  

If you look around you will find you can put a electic start trans on it easier then fitting a new motor in the frame, I have a picture of a trike that a person
in P.A. put a 3 speed trans and alum side clutch cover
off a 1976 thru 1982 hd. it had a clutch arm on it like a early panhead  if this will help you ,I have two trike one with a stock electric start trans and one with out  

freewilly409:
If you look around you will find you can put a electic start trans on it easier then fitting a new motor in the frame, I have a picture of a trike that a person
in P.A. put a 3 speed trans and alum side clutch cover
off a 1976 thru 1982 hd. it had a clutch arm on it like a early panhead  if this will help you ,I have two trike one with a stock electric start trans and one with out

Thanks for the info. I've been looking, but they seem to be scarce. I'd appreciate any leads that might come your way.