starts fine, smooth idle 30secs, rough idle, then dies

Back to basics. As stated earlier by another poster, as it gets ready to die spray a little starting fluid in the throttle body. If it picks back up you know you aren't getting fuel. Some early P30's had two fuel pumps even with TBI, one mechanical on the motor just like the earlier Quadrajets, and a electronic pump in the rear but not in the tank like most fuel injected motors. If it has this setup, the back pump may not be working correctly.