Farmdreamer, Those were built in my hometown Longmont. I have an unrestored one that I haven't gotten to yet. The Wisconsin AEH is the correct engine, however, Gibson was notorious for using whatever he could get his hands on, ie. transmissions, rearends, etc. So I'm not certain if yours is a replacement or not. Most of the early ones came with tiller steering ( a lever that you pushed forward to turn one way and pulled back on to turn the other). I am guessing that the steering wheel is a modification. The serial numbers were usually stamped on the top of the "C" channel on the right side below the engine. That is kind of a moot point, because records were burned and I don't think there is a database that will tell you what year you have. Hope you enjoy it.
"We don't need to think more,
we need to think differently."