i once looked at an mid 80's ujm. it was crusty, dirty, and tired looking, so i thought this is perfect. after talking to the owner he said the forks were bent and needed replacing. so i looked into new forks, 1500 bucks..ef that.
you would be better off buying the forks from a more modern bike, if they dont fit with simple bearing swaps you could swap stems on the lower tree. most can be lathed apart and rewelded. somthing i personally would leave to a proffessinal..
good luck