Just had built a 383 stroker
GM 1 piece rear main seal block
Eagle Rotating assembly kit (4.030X3.750 5.7 Rod, -18CC inverted dome) PN: Eagle B13004L Eagle Street and Strip Rotating Assembly
The kit came with everything including harmonic balancer and flex plate. I didnt need the flex plate because the transmission is 4 speed manual.
I used flexplate JEGS Performance Products 601250 JEGS Flywheels
Its a 153 tooth external balance flexplate for 350 chevy 1 piece rear main.
I now have severe engine vibration and gets worse as RPM increases.....