I have an old OS .32F-H heli engine that I've run in a couple of different planes over the years with no problems. The only difference with this engine between it and the airplane version is the cooling fins on the head, and a shorter crankshaft, which makes it hard to do a spinner+prop+washer+nut, but if you use one of the nut/spinner combos (like dubro or higly or whatnot), some of them fit under the spinner, and many metal spinners have thinner backplates than plastic ones. The last plane I had my .32 in was a biplane, so I just had the prop and a higgly spinner nut on there, and had no problems. Oh, low pitch props help here as well, as they have thinner hubs.

The only other differnece between the airplane and heli version is that the heli engine is ringed instead of ABC, but that's no big deal. Back when that engine was made, OS sold most all their engines in both ABC and ringed versions.

Now, it's going to vary engine to engine. The carb espeically could be an issue, but frankly the heli carbs usually work better and are more adjustable than airplane-engine carbs anyway.