I installed a 79 351w in my 87 fox body lx my question is. If I used the harmonic balancer and flywheel off my 91 302 ho for the swap will that cause engine distruction should i move to a 50 ounce offballance. Does anyone know what balancer/flywheel i should of used the trans is a t-5 with a centerforce clutch electric water pump carberated no electronics only 8 plug wires and a distro,water pump

 

You need the 28 oz harmonic balancer and flywheel for a 351w, period.
Your 91 302 ho is a 50 oz setup.
The 302s went to 50 oz around 1981.