LA.25's FP-.40's Tower .40's. I've seen Fox .40's with restrictor. Props/ venturi's get speed right. Many used RC engines available as many have gone to electric. FP-.35's/ Enya .35's Even Fox .35's. Almost any .25-.28.32.35 engines will do. LA .25 are not expensive and are new also ST .34. Old woodies will be eaten alive by new foamies. New ships out turn them hands down. Depends on what you want. I like oldies but newer planes are much better. Have fun,Dan

You might find out what rules they are planning to use.  AMA rules ted to result in a lot of midairs, which you might not want to do with vintage airplanes.  Multi-round contests, with appropriate rules, tend to be a lot gentler on equipment.  Went to Roy Glenn's airwars meet a few weeks ago.  14 flyers, 28 matches, one major midair, one minor midair, and one line tangle crash.

I agree about finding out the rules but come on are we becoming afraid of a little mid-air collision
after all thats what attracted me and most of us to COMBAT isn't it?

The thrill of the hunt, peck and attempt at getting a "kill"
toughen up guys like we used to be...

I've always viewed 70, 75, and 80 MPH combat as an outlet for old engines that aren't good for anything else. 

There should be a rule against BUYING an engine for speed limit  or WWII.