There's always the option of buying a set of swap-meet or inexpensive new headers, then cutting and reworking as needed. Look at as many pictures of the TTi headers as you can find and kind of eyeball what they did. You can get them ceramic-coated for a couple hundred bucks after you make them fit. I'm not saying that's necessarily the route I'd take since fabbing headers is a pain, but it's a less-expensive option I'd definitely strongly consider. $900 is obscene. Even having very-few financial obligations and a good-paying job, I'd balk at that number. TTi also makes shorties that fit an RB A-body for a couple hundred less, but if you're truly going for all-out power those aren't the answer. Even a homegrown set with ~36" tubes would outperform them. Shorty headers create all sorts of nasty reversion pulses and don't scavenge worth a damn, equal-length or not. Not sure what your plans are for a transmission (I don't remember) but if you're going manual you'll need TTi's countershaft.
Just tossing out ideas.
You realize if you do a big-inch turbocharged small-block for the other car (correctly) it's likely gonna outrun the big-block, right? Last I'd heard, dizuster over on the turbo forums was in the mid-9s with no intercooling with what's basically a stock 360 Magnum longblock running E85 with an eßay Chinese S480 copy... carbureted. :dance: Of course, unless you're buying it from a controlled source, i.e. by the sealed drum, E85 can be a slippery slope. The actual ethanol content varies by season and region, which can play hell with your timing and A/F ratios.