That is a good looking cruiser for the price. Few things to check just from pics i see.
1. start and let the engine warm up. make sure the header does not leak at the engine. (lot of complaints of this)
2. check the drip edge of the roof, IE take the rack off and check the body putty (sorry forgot technical name) mine is cracked and lets water leak in car. not a major issue if it is, just something to add to the short list to fix before it becomes major.
3. rear frame crossmember. drop the spare if there is one and check up in there. the crossmemner is riveted to the frame metal on metal. There can be rust inbetween the layers and you will see if the metal is not straigh. (there are a ton of threads on this with pics. search and you will understand what i am saying better.
4. rust areas. lower rear quarters check for mud and rust. lower doors wheel wells and the tailgate are all common.
some things to take into consideration. I am not sure of Raliegh smog ruled but a header does away with most of it usually. so see if he has the parts to go back to stock. see if he added an idler instead of smog pump or devaned the pump. (if the pump is on motor see if it has suckion on one pipe and blows air out the other)
once the motor is warmed up also check carb cooling fan. (makes restartes easier(no vapor lock))
check headlight waqshers (neat feature(only seen one truck with working washers))
check front axle for leak and front end for play. may need new tie rods and axle rebuild kit (not deal killer but just something for to do list.)
Damn that got long quick.
Take lots of pictures and good luck
Dave