I got some NOS seat material from SMS Upholstery and had my upholstery guy replace the center section on the driver's seat bottom. The center seam ripped a couple winters ago when I made the idiotic move of kneeling on the center of the seat to get something in the car. NEVER DO THAT ON A COLD VINYL SEAT!
The NOS material was dated 1975 and matched perfectly.
I have around 600 miles on the rebuilt engine now. Still runs a bit warmer than it used to, but eventually it should cool down (by winter time, I guess).
