They are decent cars. Certainly lack the collectibility of an E body, but can still be built to run. IMO, a $3k slant six car had better be immaculate and run like a watch, but these are going up in prices and I'm a cheapskate. They used to be $500-1000 cars in running condition. Limited edition versions like Super Coupe or Kit Cars can now sell for upwards of $15k. Decent versions of Road Runners or R/Ts can be $8-10k.
Are you looking at it for a driver or future mods? Small blocks bolt in easy, but big blocks can be shoehorned in with minimal effort. 8.75 rears can be installed for some gear strength. By 1980, most of the weak points in these had been addressed by the factory and they were decent cars. However, the bent torsion bars are a bit weird. Firm Feel does sell bigger sizes for better handling, but they do not have lighter weight versions for drag racing. Iso-clamp rear springs are a pain and all the rubber isolated mounts should be eliminated, IMO.
