Actually:
LS2 crate complete <$5000
LS7 <$13,000
As far as manageable power, my GTO has ~480 rwhp @ 7psi and we'll adjust boost/tune for ~550-600 rwhp with the boost controller. Car is my daily driver. Yeah, I don't use all of that power very often, but it is fun!
My 66 'vert [which I've posted pics of our work to allow 17" x 11" rear wheels under the stock sheetmetal] should have at least 500 rwhp w/ 331 forged stroker [sportsman block] w/ AFR's, plenty of cam, KB blower pullied @ 12psi. But that will be a weekend cruiser, occasional run down the strip sort of car. Vert will never handle without a full cage, and that is NOT in the plans.
The 2+2 [if I build the car rather than selling it and building a GTM kitcar] will have a full cage, road course suspension, and a LOT of horsepower. It would be street driven as well as driven at HPDE and open track events. A lighter engine up front makes a HUGE difference in these cars, as does moving them back and down as much as possible. Big block Mustangs do not handle, that's for sure.
I get such a kick out of the whole brand-loyalty thing. GM just never built a car I wanted until they imported the Holden, and it is truly a marvelous car. Think BMW M6 on a budget. Seeing the kind of horsepower that can be made out of the LSx engines at their light weight, using it elsewhere has intrigued me. As far as cost, 5.0's are MUCH CHEAPER to get parts for, trust me. Just check the price difference in cams between the two. All of the LSx people complain about the cost of parts. Good aftermarket heads are ~$2200+ for the LSx engines.
Honestly, I don't think I would actually do this, but it is something I have pondered...and still could justify this FAR easier than a 4 cylinder, Ford or otherwise. Glad that is makes sense to someone, but for me, these classic cars need MORE horsepower, not less...and more rubber, more suspension, more stereo, more seats...
One other thought: engine swaps between brands are a no-no. Good thing for the GM guys that Ford 9" swaps have apparently been approved by the CAPC [Committee for Automotive Political Correctness]!