Well, the only small block headers I've used on this body style are Hooker Competitions. The 1 5/8" primary model. They fit really well and didn't require any clearance of any sort. Flanges were also pretty thick and never had any issues with leaks as long as I stayed on top of keeping the bolts torqued on the Eddie heads.

I bought them ceramic coated and that didn't last for crap though. Got one season out of it and all the car saw was fair weather summers.

While they fit really well, they are a complete pain to work around.

Think I paid $350 for the coated version. This was almost 15 years ago.

I think another M guy here has TTI on his Dippy cop car though. Maybe Larry will chime in.