Details are still coming in, but here's my vision so far. My main criterion is that it can be DRIVEN, regularly and reliably. Not that I'm planning coast-to-coast trips or anything, but I do intend to enjoy it in motion. I don't care if it's loud and cramped; that's part of the package (though I've got to watch the pedal spacing with my wide feet).
I've always done cars the way I like them. I've never been into 100 point show cars with all the proper chalk marks and fasteners. I'd rather have black residue on the rear quarters and dead bugs in the radiator.
To give an idea, my target GT40 might be a Mk I body with a 400HP carb'd small block Ford, an appropriate reliable transmission, and a/c.
I'm starting with a budget in the $50-$60k range and seeing where it takes me. I might pay more in some circumstances, and I'd expect less for something incomplete or needing work. Example: earlier this week an early 90's KVA kit with a 302 and Porsche 914 transaxle went for $37k on eBay. Seemed to be in nice shape with new paint, but it did need a few things. This is the type of thing I'd consider (though I need to do more due diligence here).
I'm very open to suggestions, cautions, recommendations, etc.!