Do you know whether it is the first run that had balsa sheeted foam wings or the last run that was all built up in construction?

Both are good, but the foam one is a bit heavier.

I had both kits, both flew well built per the instructions. The landing gear is a little short if you want to go with props longer than 21". TNTLanding gear can fix that. Had a BME 50 on mine, and it flew very nice but I've gone on to bigger planes.