Don't think I'm going to have much good news for you. mines a 70 and I've been using BT "B" heads for years now. Here's what I had to do to the shock towers to fit my headers.
those are 2 1/4" primaries, I fear even if you try 2", or smaller, you'll have to dimple the shock tower just to get a set in there. I had the 6201 hooker headers with factory heads and they fit with no shock tower modifications but you still had to cut a hole into the right wheel well along with requiring manual steering. the 1 7/8" hookers are nearly a direct replacement but will not work with the bt's.
If someone was to custom build a set of headers, a 2" MAY fit with no shock tower modifications. $3000 seems a bit steep for an exhaust system unless it's stainless.
I used to have mine set up with factory mounts but have since fabricated a motor plate to get the bit tube headers to fit
If I can help, pm me with questions
Dave[/code]