[slowbird]

We have a set of round port JR headers that fit our 65GTO, any chance they'll fit our 69 GP?

[Tom Vaught]

Most of the difference in the cars appears to be due to the extended sheet metal forward of the front face of the block. Palbykin had a 428 car that seemed to have about the same firewall clearance as a GTO.

The JR Headers were very good headers. Had a set on my 64 GTO. They were made in Michigan.

Check the passenger side exhaust first.

Tom V.

[steve25]

I had a 65 GP that I thought the headers for a A body would work on and I was lucky enough to have a trash set of the A body ones to try out in the GP.

The drivers side would go in, but it would limit the steering some off the end of the pitman arm by coming in contact with the front most tube.

The passenger side would not work at all so I gave up on getting headers in that car.
Some 6 months later I got told that a early set of F body headers would have been a drop in.

To this day I don’t know if that’s true, but I think your 69 B body is still the same as my 65 was in terms of frame and steering parts .

You need to investigate more to be sure.

[242177P]

Originally Posted by steve25

... but I think your 69 B body is ...

69 is a G. It's really an A-body with an extended wheelbase (3")

[slowbird]

65 a-body is different than a 69 a-body right?

[242177P]

Originally Posted by slowbird

65 a-body is different than a 69 a-body right?

True, but picture a 69 A-body with the engine setback
far enough to accommodate long branch manifolds.

[slowbird]

So yes they might work?

[Tom Vaught]

YES! 65 a-body is different than a 69 a-body right? 69 GP IS an A-Body.

Tom V.

[Tom Vaught]

65 a-body is different than a 69 a-body right? NO

69 GP IS an A-Body.

65 Big Car is NOT THE SAME as 69 GP body

Tom V.

[242177P]

Originally Posted by slowbird

So yes they might work?

Unless there's something really unusual about the firewall, I fully expect they would. Clearance around the crossmember is what separates 64-67 from 68-72.

[b-man]

The 1969 GP chassis is unique in the way you can fit both long-branch manifolds intended for F and B-body cars as well as Ram Air/HO manifolds intended for A-body cars.

They use the same motor mounts as a first-gen F-body. The engine sits a full 6 inches back from the front crossmember, the G-body 1969 - 1972 GP sits on a 118” wheelbase modified A-body chassis, stretched 6” ahead of the engine so the engine sits against the firewall exactly like it would in an A-body car. A 2-door A-body rides in a 112” wheelbase starting in 1968, 4-doors on a 116” wheelbase.

Only the first few years of the G-body GP had that special 118” wheelbase. In 1970 the all-new Monte Carlo also had a special long wheelbase chassis for its 2-door body but it was only 116”.

You can use whatever A-body or even first-gen F-body headers or exhaust manifolds you like.

[Sirrotica]

FWIW, a 69 GP is a G body, not a B body. It's made on a stretched A body chassis with a engine setback roughly 6 inches. 1969 was the first year for the G body, and Pontiac had the first year all to itself being the originator of the concept. Chevy didn't get the platform until 1970 for their monte carlo.

I used A body D port headers on my 69 GP dirt track car, I have no idea what brand they were, but they did fit. That was in 1977-78 so it's been way to long to remember what brand any longer. plus they were used headers when I got them. The third picture in my signature pictures, is my 69 GP SJ 428 dirt track car, just to clarify what body the OP is asking about.

Setting the engine back in the chassis opens up a lot more real estate than a conventional A body chassis has. The firewall, and the passenger cabin are moved rearward the same amount as the engine setback.

The engine setback was a plus to get a better weight bias from front to rear, an asset on a car that is intended to go around corners at speed.

[steve25]

I bet they where Appliance brand headers back then as they where extremely popular and made decent.