[stevep]

The stock 2 bbl manifolds will work for single or duals.
The car will be happier with the duals.
See if you have a local custom exhaust shop.

[63RedCat]

You can put a Pypes exhaust system on your 65 Cat, however you will have to modify your cross member to do so. The standard Pypes exhaust goes straight back and the Cat exhasut turns in toward the driveshaft quite a bit. I put one on mine and had to rework the cross member. The tail pipes that come with the kit will not fit at all. I sent a set of tail pipes to Pypes to use as a pattern. Should have the samples back this week. I also installed the HO manifolds at the same time. What a difference! Good luck with your project.

[lust4speed]

I believe that the left center exhaust exit is the correct one for both single and dual exhaust on the 65. After ordering and playing too many games with the kit suppliers, next time I will go straight to the custom exhaust shop. Won't probably be any more money all together and no headaches.

We added headers later and that really gets interesting with the stock 65 crossmember. We cheated - bought a 67 GTO convertible crossmenber off ebay and added about 3" on each side and just added a little bracing. Now have 3" extensions coming straight back from the header collector back to the cutouts and the 2.5" X-pipe. No-one notices the new crossmember unless I point it out to them since the center section and the area around the pipes is Pontiac correct - just a different year of being correct. Other mods I have seen done scream out that there has been a massive alteration to the crossmember. I would bet that a 67 big car convertible crossmember would have possibly fit with no extensions, but gave up trying to find one since we had a Pontiac points race coming up and needed to get it back together.

[Deadhead]

Originally Posted by lust4speed

We added headers later and that really gets interesting with the stock 65 crossmember. We cheated - bought a 67 GTO convertible crossmenber off ebay and added about 3" on each side and just added a little bracing. Now have 3" extensions coming straight back from the header collector back to the cutouts and the 2.5" X-pipe. No-one notices the new crossmember unless I point it out to them since the center section and the area around the pipes is Pontiac correct - just a different year of being correct. Other mods I have seen done scream out that there has been a massive alteration to the crossmember. I would bet that a 67 big car convertible crossmember would have possibly fit with no extensions, but gave up trying to find one since we had a Pontiac points race coming up and needed to get it back together.

You might be able to use an open frame crossmember if you went this route. That should be about 3" total longer. Would probably have to modify the ends.

[lust4speed]

We had an open frame 67 GTO hardtop cross member for comparision. That sucker was almost a foot longer than the width for the 65 Cat piece - plus we needed that one to go back into the 67 so we didn't want to cut it up. Really surpirsing how much longer the open frame cross members really are, and shortening them presents other problems since you get into the angled U part of the cross member really quick.

[63RedCat]

Here are pictures of a Pypes exhaust on a 65 Catalina. Had to modify the crossmember to fit. Turned out well though. Used Race Pro mufflers, nice rumble.