Only 5100 hours...
My 67 G model has over 6200 (3128 on the current tach, the third).
For what it's worth, Here are few of my thoughts:
1) Where's the aircraft? If its not at home or this is being done at a distance by an unknown mechanic? If its at a distance, I'd try and bring it home if its airworthy. If it's at home and you trust the mechanic...
2) The questionable auto gas STC is no big deal since at worst all you have to do to be legal is drain the tanks and refill with 100LL (I'd probably just fly it and refuel with 100LL as I go.)
3) The G through K models are my favorites, you get to sit in a reasonable position and they have the bowed out doors. The flat gear are a little stiffer and narrower than the tubular gear introduced in the Ls but if you can grease a landing with the flat gear you know you're doing well.
Good Luck!
