Well, small update, I emailed the seller I had in mind and got a few things clear, the body had only paint worn off, so the ridges were just fine. Also everything on the body worked as it should. The Zeiss 80mm was flawless optically, and the shutter speeds seemed okay to the seller, so after checking with my repair technician (great guy, gives appraisals for free for analog cameras, repairs just about everything and has been in the field since the middle '60s, when he started working for the biggest camera workshop in Finland), I went ahead and bought it. I would have taken up some of the offers here, but since this combo went for less than 700 dollars I thought it best not to waste anyones time, since I'm a bit strapped for cash and this helped me avoid a 25% sales tax and a 25% import tax (everything over 50 USD is subject to at least a 25% import tax if it comes from outside of the EU).
But, now I need a finder, strap and an A12 back. I have found some good ones, and have put a bid in for one on ebay, but if anyone has a A12-back (preferably black to match the body) that's in good condition, I'd be interested.
Also, how hard is it to replace the winding knob on a 500C/M with a late model crank?