FPA make an awesome set of headers for a 70 Mach1's 351w stroker. I have a TCP R&P steering, Quicktime bellhousing, 418W with AFR205 heads that have wide bolt holes. They fit perfectly and the quality is top notch. Stan is a good guy and welcomes phone conversations to make sure they are right for your setup.
I have a set of unused hooker comp they are 1 3/4 x 3" collectors. Bought them for
my 1967 fastback GT when i ordered them from summit racing they. Specified a certain tower separation for proper clearance
Over the years they tend to close up.