hope you find this. on my 69 firebird when the electrical system shorts out its one of two things. there was a loose power wire to my starter that would kill it dead. jiggle the wires and that had a bit of a routing problem being sqeezed between the exhaust manifold and the engine mounts and would come back to life. leave the door open when the dome light comes on you know you got it. or if lights still working  check the ground to the distributer. oand safe to say look for any bad ground or loose contact. for the first problem a new starter solinoid combo proved that mine was worn out more than originally thought.  

want any more comments on your 301?Finding a motor probibly is not as easy as 10 yrs ago when I was chasing ponti. motors.I always looked IN WANT ADS AND PENNY SAVERS FOR old pontiacs for sale67 to 75 big pont. was aperfect place to start.the engines were all350 to455.I know all real ponts bolt in with stock motor mounts. for the car body you are using.ames performance .performance years are 2 good places for catalogs. Also P.O.C.I. is agood natinal club for pontiac owners to be involved with. phil the geezere