The core support may no longer be available new. You'd either need to have that one straightened or find a donor to cut from and get it welded in by a qualified welder. Both of these can be MUCH cheaper if you get all the prep work taken care of before the craftsman takes over.
Either BTWilson or Bill UK posted the Supra chassis measurements from Toyota's Collision Repair Manual... If you're interested in seeing how far off it all really is.
At any rate, given the time I'd have to put into it, not knowing how true the rest of the chassis is, not knowing if the bumper support or sub frame were damaged and not knowing how it's running, I wouldn't offer more than $1000. Given that it sounds like you've had overheating issues (that wasn't clear) and that you say the interior is in mediocre to poor shape I'm thinking more like $700 to $800. But this is one of those things that's always contingent on first hand appraisals and varies per the local market.
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