First let me thank all the folks that replied. I'm now in much better shape.
Well, all the old monocoat is just about off , cabanes have been de-rusted. Next will be the tail wheel assembly and then the rest of the plane.
My motor choice is still tentative, however the seller had a K&B 40 sportsman in it and reports it flew very well .
The final motor decision will be based on weight , there is a lot of light ply & spruce in this plane. Right now , it has a HAYES motor mount (AS40)in it which is 1.33" between the beams and 2.11"overall width. So my thought of the OS 52 SF at 1.33 crank case width is more of a convience than anything else. A .40 four stroke would probably be fine too.
My felling is, if the plane RTF is 5 # then the .52 is perfect . If 4# then the .40 would be the ticket for bibe type flying. However a .25 two stroke sounds weak to me. Does anyone have the RTF wieght ( any motor).

LJR