Talk me into Fenderwell Headers

Other things to consider since the 70's when fenderwells were the only choice.

The heat problem can be minimized with coatings and thermal barriers. Header wrap. Painting the floorboard and the backside of the firewall with the ceramic heat barrier coatings available like Lizard Skin etc.

Move the master cylinder over with one of the Hemi Dart repro brackets and use shielded hoses from an industrial hose maker. If I can get them in Omaha I'm sure they can be had in most civilized areas.

If this guy Is going for a stroker big block I seriously doubt he'll be flying over speed bumps or autocrossing or entering parking lots at 30 mph. Which header you choose will be dependent on what the PRIMARY goal of the car is..if maximum horsepower is the goal a fenderwell type is probably the least expensive way to get there for reasons already mentioned.

In an early A car I think I'd go fenderwell simply because I don't want to tear half the front end apart to put TTI's on a small block.

If the car is a numbers matching 340/383/440 car then I'd find a used ____ /6 318 car to hop up and leave the valuable version alone.
But it is yours so do what you want. Good luck regardless and take pictures.
Alan