I have a 62 K20. I would say the hardest parts to get would be parking brake cables and the hardware in the drums. Transfer case gears and associated parts seem rare, however all bearings and seals are available. I've done a fair amount of work - fixed leaks, brake system, water pump, radiator, front end, exhaust, etc., no major problems finding things. My truck is in fairly god condition, needs some body work, but I use it regularly, with a couple 100 mile highway trips each year.