Thanks, correct. The use of stock cast iron manifold is part of this equation. I have only found one company that makes full length header for a 4x4 V8 Colorado, which is OTTP. They are $1,000, not a "couple hundred bucks". AT $1k, it starts to make you think about work-arounds. Could I afford them, sure. But I'd want to be sure the hp/$ would be there to justify it over anything else. I think the stock LS3 is rated at 430hp with iron manifolds, and some even can get it to 450hp or whatever with tuning, then closer to 490hp with "bolt ons". I think most people agree there is a peak of nearly 50hp to be made at top end.

Let me know where you have seen your mentioned "Tri-Y" headers. The only thing I have found are Doug Thorley's, which maybe this is what you are referring to, but it says they do not fit V8 Colorado 4x4. 4x4 uses torsion bar front suspension, so that passes right in the way of most conventional header systems. Plus the V8 was rare, only 1,000 per year from 09'-12' only, so not much aftermarket support for it. It was a ridiculous $4,000 engine option, in an otherwise budget truck, so nobody really bought it. Sweet setup to have though, if you are not a full size truck person, which I am not. Full size truck engine, trans, and narrowed rear axle (10 bolt).

I asked Cam Motion about Darth's suggestion, and they just replied to make the LSA 114. Not sure if this was still the 114+4 or 114 (?).

Thanks all for the input. Sorry the stock manifold thing is kind of in the way on this one due to its uniqueness, which is why I asked for some help The cats and resonator are gone, and it is now twin 2.5" into 3". Can really feel how much lighter that made it on its feet in itself.

Ears still on if anybody else has done this or has input. Thanks.

 

Op has a 2000 converter, or so he says. I have a 215@.050 cam now on a stock converter, no issues. You could probably run a 220 on the stock converter, just depends on the intake closing and spread. Not ideal, mind you, even a stock LS loves some more converter, but functional and better than stock still. IMO headers are not a big deal till you get serious on the cams. I have seen plenty of trucks/TBSS's running 12's w/ bolt on's and mild small cams. Even shorty headers are really no better than stock manifolds. It's long tubes or nothing, basically.

I don't disagree w/ your cam selection, but for the $$$, it 's not a gain. I put a value on $$$ per Hp, and that's not enough vs stock to care about. If you have to pay for cam/lifters/springs/pushrods to make it move, go all the way the first time. Just my opinion.