I would imagine RAC would probably just check the mechanicals etc.
If you want it, go and see it, take a torch, notepad and pen, and get from it VIN no from chassis and plate (do they match up) gearbox and engine no's. and ask to see reciepts for the work. Look at the V5, what engine no is on it, does it even match up? Phone the DVLA with all these details and tell them you want to know if all the parts are legit as you are about to buy it but suspect some foul play.
I would also want to know about the old parts of the 1991 Landy it claims to be.