a friend at the air field gave me his 60 sized low wing trainer. the engine i'm mounting in it is a 70 four stroke. the rear 2 holes don't match up though, would it be ok if i just put double threaded wood scews in the rear holes. the front two match up with the blind nuts perfectly.

thanks dave trimmer

Dave a FS does have a lot of vibration if at all possable epoxy a round piece of wood or dowl into the old hole and redrill a new one for a machine screw and nut, for the engine you have a standard machine head wood screw will work as long as you are not removing it alot if you take it out a couple of times then you will open the hole and the screws will loosen up fast, its a quick way to break a engine mount the front screws tight and the rear loose.

Assuming that you will be able to install new blind nuts after I'd go with bigtim's idea. Yes the dowel is important to save strength in the engine bearers. Open the existing hole up so the dowel will just squeeze in when tapped with a hammer and apply wood glue to the dowel and the hole. Dowel needs to go full depth of the hole. Obviously knock out the old blinds nut first.