360 Flex Plate

Alrighty here we go lol

a stock 318 or 360 flexplate will bolt right on to each other. Stock 360 goes on a 318 and vise versa. That vibration you had was because you put a converter for a internally balanced motor onto a externally balanced motor. Which, talking about factory balancers, is a no-no. The factory 360 converters have counterweights on them to balance the motor.

However, you can take that same 318 converter and bolt it onto a 360 with no problems if you run the proper flexplate that is counterweighted itself to balance the motor where the factory 360 converter would go. Forged crank 318/340 would take a neutral balance converter (no weights). Stick that on a 360 with a factory flexplate and you'll get that vibration you had. Stick it on that 360 with the b&m 360 flexplate and she'll run like a champ.

Hope that makes sense