I posted a similar question on two other forums, and someone just posted pics of the Dynatech headers in a '69 Firebird with the recommended DSE mounts and 3* trans angle:
I don't have a good machine shop that I've worked with in the area. I'm going to swing by the exhaust shop later this week and see if they have any recomendations. If I mill my current flanges flat, I'll also have to dimple the headers near the PS box even nore in order to get closer to 3* on my trans angle.