the big thing are 3 +topics:
1) chassis as good as possilbe ..any real work is easily 30 kUSD may be 50. I mean real chassis work -no dents, on plaster.. all paint thickeness is the 350 to 700 micro range. (see above devices).
2) solid GEAR BOX ..I know is hard to tell as lots of stuff was siting in the garage for 20 years.. if this is the case expect app 5..7k USD as long the axels, the differential and the gear sets are good. Mostly the synch are all gone 5x 350 USD, also the limited slip disks are gone including the gear to it an other 500, plus 2 k repair work. If not you go close or bejond 10 k USD.
3) Completeness of the car and its components... this is not a GM mass production car; parts are avail in particular due to the nice Forum team folks!!!!
3+) ok the engine, understood is a US lower mass production engine, but again it is NOT A GM engine from a cost perspcive! (is a top engine ok!), so expect all x2 on cost comp to a GM. ( I am NOT picking on GM I have Corvette C2 from 67)
did go through all of this.. is a top and unusual car..and worth it.
Happy to help..
Matthias