Ken, I don't think your 200 lbs of weight is much of the issue (heavier springs), its the extra 350 hp thats gonna make a difference. I just restored a SS Chevelle about 6 yrs ago, the SS had heavier sway bars (front & rear) boxed trailing arms and a 12 bolt rear end (on the suspension & frame), I almost forgot the SS also had disc front brakes, stopping a big block with drums is harder to do as well and with that much hp probably not wise. None of the above was offered on the 6 cyl cars so I would think those parts would need definetly upgraded, keep in mind the LS6 was a bad boy no question but still was not 650 hp + a shot of nitrous! Have fun, do 'er right once and you won't regret it, these guys will keep you straight.