My TQ build 383 was 400 lbs at 2500 and just shy of 500lbs at slightly over 4,000.It is 375 at 4500.
LS3 I would have to be very lucky to find a wrecked 2008 Vett will a willing seller that didn't want a fortune for it.It's kewl to pick out a engine here,but the reality check happens when you go for the wallet to pay for it.
The thing I do is I look at the aftermarket for problem solvers in the parts they offer to understand what might be a issue.One common part I see is head gaskets for these or to be fair about it some of the LSx engines.Is that a problem??. Also in the aftermarket blocks some of the features they offer to maybe cure OEM design weaknesses,but there again,that might be just because of the extra stress of power outputs that I would never approach.
I did read about the limits of the OEM head design/rockers for enough space under the rocker covers for a high lift cam.It seems a good set of heads would be in the range of $1,800 to $2,000.
But I an still curious what you guys think was the one thing GM improved on the LS engines that make them perform as they do.