I have 1-7/8" Hedman Hustlers with 3.5" collectors (for d-ports) in my 79 T/A and they require an adapter plate between the header flange and the cylinder head.
I'm never buying another Pontiac header that doesn't require this adapter.
I can set the engine on its mounts and slip the headers in from underneath AND be able to get to ALL of the bolts with a socket or wrench. With the enlisted help of a friend, we had both headers on the car and snugged down tight in about 20 minutes (not kidding).
I've never been able to do that with any other header.
