Mine is doing the same thing... about 10k miles on a rebuilt 360, new balancer, flexplate, TC, new 904 trans, mounts, belts off or on, park and neutral it still vibrates.... timing is good, oil pressure is good, no rattling noises, been doing it for a while... no drop in performance, just a harmonic-type of vibration around 2 grand.
is there anything on the inside that can go bad?? That's about all that's left on mine..
