There is restoring to look nice and drive it around and there is restoring that it is so nice you don't want to start it ever again and just hang it on the wall. Is it going to be a surprise for your Dad or is it going to be a Father/ son project? Do you think Dad wants to drive it once again and get out on the track and is he healthy enough to do it? I see guys a the vintage meets today that can get in the kart and drive it once again but then getting out of it is an ordeal and they say "that was my last ride". Hard to ask Dad if it is going to be a surprise but if not then chat with him and see what he wants to do. You have most of the pieces needed and you live in the area where you can find the ones that are missing. There are plenty of Rupp karts there in Ohio and I know a lot of guys that would give you a hand if asked.
restoring it to look nice. He's collected cars and restored a couple to the point where he didn't drive them, then they sat and, basically, needed mechanically restored after sitting for 20 years looking nice, but not being run. I will run this. He also got a pair of early mens and women's 1920s/1930s aluminum bikes...and those needed restored. I found a place in Wisconson that restored them, and, after getting the quote (wow), I was still in, and said we'd be looking forward to getting them restored to ride around on Saturdays...and was immediately told, oh no, you can't ride them...the aluminum is too brittle, they'll crack. It's just to look at. Yeah, that was the end of that, they're still unrestored in the garage, I like to use my toys.
My Dad will probably cruise around a parking lot in it, but he wouldn't race it (my son, daughter, and I all would). He plays tennis a couple times a week, so he could drive it...but I don't think he'd want to race. I used to drive at the track, and he DID NOT like going on hot laps.
Thanks for all the posts...looking forward to getting the project advanced a bit.