I don't run poly on my '68 truck because no one makes poly for it (not actually 100% true. Imperial Services makes the trans isolator but they haven't been able to figure out how to keep the metal from delaminating from the poly but its a quality issue with their parts and not poly in general).

I do run poly in my '86 Daytona Turbo Z and it is actually annoying. I only switched one of the three isolators and I won't be doing the other two. But the 2.2L engine was always known for vibrating like crazy. I don't honestly know what it would be like on a V8.

I hope to find out soon though as there's a chance one of the Poly locking isolators made by Poly Bushings will work as an engine mount for my truck. Right now I have the engine strapped down with a chain. It is the only way I can keep from breaking engine and trans isolator.s