OKay, so we pulled the V6; the V8 is at home in my Firebird's engine bay. We got it all hooked up to everything, and spent a helluva time making the wiring harnesses from the '91 camaro 305 match my '86 firebird ex-v6.
So we "finished" and we decided to try the motor out. Well, we came up with two problems:
1) The 305 isnt getting gas - hypothesis: v6 tank cant handle the pressure, swap in z28 tank
2) Engine wont stop cranking - hypothesis: we screwed something up; bad starter solenoid, ???

We were able to start up and shut down with no probs twice. The third time, we weren't able to stop the cranking. We pulled out the key, still crankin; pulled out some fuses, still cranking. I had to disconnect the battery to shut her up. So what were going to do is set up a kill switch untill we can get this issue solved...

any ideas on any of the above?

 

Your Bendix spring on your starter is prolly the culprit.

 

Try changing the fuel filter. I am not sure the tanks are different. You might be able to get by with a fuel pump swap.

I also agree that there is a problem with the solenoid or the spring that returns the starter srive from the flywheel. Are you using shims?