You need 307 frame mounts. Any 73 and up Non Trans Am or Omega rubber motor mounts will work, small or big Olds block are the same. What trans in the car? What trans is attached to the 403, TH350 or TH400? I would do the oil pan and rear main while the motor is out of the car. The rope rear main seal can be a pain to remove. There are two rubber rear replacements available, either the reboxed Ford 292 or AMC 6 cyl seals that just needs "ears" trimmed to fit and fits tighter. Also do the timing chain, a mild cam would also be cool but requires removing the intake. Also do the valve covers. Rocket Racing has nice reusable, rigid core rubber valve cover gaskets. Also dual exhaust is a very good idea. There is a block off cap available for the manifold's extra outlet.