The compression on a stock VW motor is right around 8:1. Have him send you some pictures of the motor. 1966 cars originally were 6v cars and only in 1967 they went to 12v systems. This doesn't really mean much unless you want a radio or headlights you can see with at night. I would raise the ass end up on that thing a bunch and put a real tire under it so you can utilize the freeway flyer gearbox if it really has one. A freeway flyer gearbox could mean a bunch of different combos in the gearing. Like a smaller ring gear or a taller 4th gear. I used to run a 1600 single port with a big cam and some mild head work with a 3.88 ring gear and .84 forth gear from a type 3. My bug would cruise at about 70-75 at 2800. The only issue was the gear was so big you would have to wind third out to get it to pull fourth and if there was any hill or breeze I would have to slow down or shift to third. I also used to run a 205x75x15 tire on the rear. Let me know if you have any questions. I have been around VW my whole life and know a thing or two about them and making them fast.

I'm not sure about compression psi numbers but if they are all close to the same then you should be good. On the motor I would look for the rubber boots that connect the end casting to the intake manifold. If they are cracked the motor will run super lean. I would make sure that a lot of the tin is still around the motor like the front and rear plates. Those help cool the engine believe it or not. Also if you do get it get rid of the deck lid stand offs. Those make the motor run way hotter. As far as the way it runs it's hard to say what to listen for, VW are noisy, the valves make a shit ton of noise.