I have a pallet of LS engines coming across the pond as we speak.
my own thoughts are .....
highly-strung 4-valve engines are fine and produce the power they're designed to, but they all come from emmissions-land, so you're never going to find one with decent horsepower in standard form. Tuning only chases the peak power speed upwards, so that's out. But all this is quite literally blown into the weeds by any of the fuel-injected Chevy motors, even the earlier LT.
Consider :- for my £5000, I bought a Holden GTS with an LS1 already fitted. I challenge you to find me another car which will carry five people with ease, will pull away from traffic lights in sixth gear, clear six seconds to sixty mph and return 32mpg without trying. (not all at the same time, obviously). As well as that, it sounds like the approach of the four horsemen of the apocalypse. My mates at the last trackday I did in it reckoned that it was just about the most butch car ever built.
The biggest problem I have is that if an LS1 Omega is to be built, it must come in under £5k or so, otherwise you might just as well go out and by another Holden, no ?
Technically, I think its no real problem. I'm certainly not concerned by the steering box issue or cooling. I've got a good recipe for rear axle, driveshafts, brakes, engine and transmission. For what its worth, I'm not sure that the Tremec T56 is the way forward, there are better solutions in T5 and TR6060 with much superior change quality.
Happy to do a deal on my spare LS1. I'd actually be quite happy to build the car for you.