Good feedback guys, but perhaps I had better clarify on the issue, this 355 I had the problems with and breaking dampers, we tracked it down to the vacume secondary Holleys secondary stages hanging open a bit after I got my foot off the accelarator. Cured that problem by putting 2 holley 650 double pumpers on, bingo no more backfires. I sold that car on a few years back.

Now I am building up a sleeprer Holden HG ute, built the motor up and everything................ Then I changed my mind, going the 383 stroker motor with the internally balanced crank and a nice big 6 71 hanging out the bonnet, I will be using 2 Edebrock 1405 600 cfm carbs because they are nice and compact. so much for the sleeper idea when you want to have fun. Still got the original 350 it is going into another project. I only raised up the idea of running a vibration damper verses a steel hub because of the longer stroke of the 383 3.75" as against the 350 3.48" strke was with the longer stroke would there be more Harmonics happening lower in the rev range ? And I will be driving the blower 1 to 1 so that will be putting some mofe strain on the crank snout and harmonic balancer.