At that point just get a LS7 crate to get the car on the road, rebuild the LS3 and sell it. You won't get squat without a decent motor, you are money ahead to fix it first rather than take a hit on the lack of an engine, you may find someone who will want to either engine swap etc., but they will low ball you all day long with a bad engine. IMO of course.
Plus if you would buy a new Z/28, just to swap out the hood and front bumper, what's the point in getting it? I mean your suspension set up and custom bumper and hood etc. already set it apart, get the LS7 crate and you're set.
Sorry to hear Jay, hopefully you find a equitable solution.