Just getting back flying after 40 years. Re-starting w/a LT-40. Flew it yesterday and flew great except wants to climb at all throttle settings. (needs down trim) I'm thinking of shimming the trailing edge of wing. Is my thinking right?? Its surprising what you forget after 40 years.

That would be correct. You could also add some down thrust to the engine.

I'd go with shimming the engine. Simply place a washer behind the top two screws, but behind the engine mount. That will give you a degree or two of downthrust.
Dennis-

If I were to add down thrust would it not still need the same down trim as I have to give it now at idle???

With a flat bottom wing, the faster it goes, the more lift it generates. With down thrust in the engine, the harder the engine pulls, the more it tries to pull the nose down, thus counteracting the extra lift of the wing (to some degree). You won't completely overcome the wings desire to lift, but it will help a little.