It'll Work Lanse

I have seen two of these engines with headers at tractor pulls. The difference in what they did and you are thinking about was that they also fabricated the intake as well. They had used a flat bar stock 3/8 inch thick that bolted to the head with the ports cut. The 1 1/4 inch exhaust tubing was welded to the flat stock. You can buy U shaped exhaust tubing that you cut into different sections to form the direction needed then weld them together.
The problem I see using the old intake would be to get the exhaust bends out from behind the center of the old intake. The distance from the head would not a problem as long as both are the same.
I would use a plate to the head and use extension pieces from the old intake to the plate bolted to the head after the exhaust header was fabricated.

Quite a project without a machine shop but there is nothing like doing it without those tools. A lot of headers were made by brazing the pieces together. The mounting plate holes for the ports could be torch cut small and matched to the head with a air grinder. You need one of the heads back that you dropped off to use for assembly of the parts as they are made. Richard might have a junk head thay you could work out a deal on that would be closer.

Fun project.

This is a header kit place with pictures of the U bends. Click on the pictures to enlarge and see what was made from the pile a parts.

Food for your thoughts.
Header Link

They only seem to have the 180 degree bends in the 1 1/4" Probly only take two.
Link

It might be more of a way to fill in the understanding gaps.
Nudder Link