Hi guys,

im doing a friends 76 Monte at the moment. It’s a minty fresh 80,000 mile car. Fully loaded model with swivel buckets 350/350 etc. Does anyone know a header model number that fits these cars properly? I see lots of headers listed to fit but I’m scared to order them and run into poor fitment. I will post pics soon.

in the meantime here is my buick

 

First off, you'll need to change out the transmission crossmember in order to install true dual exhaust, something like Summit Racing SUM-770322.
I used Hedman Hedders #68290 in my 1974 Monte Carlo with a SB 350, cast iron phase II bow-tie angle-plug heads, stock suspension and steering, factory a/c, and automatic trans.
These headers installed with less hassle than I expected.
The instructions said I needed a minimum of 36-inches clearance and I needed to unbolt the engine mount on the driver's side and raise the engine on that side two-inches so as to install that side's header.
I only had about 16-inches using jack stands. To my delight, the driver's side installed with no hassle or dimpling. I had to remove the starter to install the passenger side header. It seems to me if I had 36-inches of clearance, i.e., a hoist or pit, I wouldn't have had to remove the starter. On top of all that, there's no interference with my angle-plug heads.
If your application has AC, I recommend you get a Hedman Auto Air Conditioning Bracket, #20110, and use Proform Self-Locking Wedge Header Bolts #66753. They use Nord-Lock wedge locking washers. I've had them on my car for nearly three years and they do not come loose.