Those look like my ProParts big block A body headers in design. 1 out, 3 in. I had to section the outboard pipe in a little and mod a lower bend of one of the runners to fit a 451 in my 65 Barracuda. I made a set of 1 3/4 LA headers for same car out of a set of 67+ Hooker Race headers . Just rerouted 3 primaries. a chop saw is your best friend and I bought some Hooker butt-fit rings, sort of a ring with a flange on both sides to center the pipes while welding. Learn TIG, flux core (!) and gas are very hot and burn through old pipe very easily. New pipe is alot easier but still had some burn throughs.
