every single inch of the chassis needs to be checked unless youre replacing with galvanised as a very rotten chassis can be very frustrating as you keep finding more and more holes even after you think youve finished patching.
especially check the front legs, all crossmembers (not too hard to replace) very front spring hangers and very rear spring hangers. and the bulkhead at the top corners, pillars, top rail and footwells
mechanically, check for oil in the water vice versa, test drive it. make sure it doesent pop out of any gears which again if your rebuilding the vehicle wouldnt be too hard to fix. the engines are usually pretty reliable, but check for excessive oil smoke, expect a reasonable amount especially upon startup. check the feel of the steering and operation of the brakes. these two things will be refurbished anyway during your project but its always better to start with better.
while driving press both accelerator and brake at the same time, and see if the clutch slips.
park it on the flat with hand brake off and out of gear. make sure it AINT moving as your going underneath it. wiggle the props at both ends and check for play in the UJ's and in the diff/gearbox too. check brake pipes and fuel lines etc.
and DONT forget to kick the tyres! then hell know you mean business. and offer him at least 10% less than what he asks if not more but without sounding cheeky.
