1987 and up are all roller cam motors. 1986 and under are flat tapped cam motors. That is a fact that I've found from several resources. So if you are looking to use parts from a 305, you want an '87 or up for your 9c1.
1990 9c1 Chevrolet Caprice
Mods: Rebuilt 350 at 169k bored .010 over (351ci total displacement), Dual Exhaust with Flowmaster mufflers and a summit high-flow cat, 700R4 rebuilt with strengthened high gear clutch pack and a new torque converter.