69 GTO Ram Air Exhaust Manifolds

[cnibs]

Any ideas or recommendations on sealing these manifolds. I keep loosing the seal at the rear port on the pass side manifold. What is the best exhaust manifold gasket to use?

[MrPbody]

The factory used no gaskets at all. If the manifolds are "flat", and the head flange is in good shape, you should have no issues.
First, use a straight edge to determine if the manifolds are flat. If not, have them resurfaced by a competent machine shop.
If it's at all practical, remove the heads and have the exhaust flanges milled.
The ONLY gasket that will work with the iron manifolds is the steel "shim" that comes in all the stock overhaul sets. Header gaskets will fail very quickly, regardless of manifold/head condition.

On my 1972 LX LeMans I had a problem like yours, however I did not have the end bolts to help seal the engine, however I was able to fix the problem with the set of steel gaskets the above talked about, just make sure you use a jack to balance the manafold and pipes or you will cock the whole thing and might make things worse by maring up the area.
You should do what the above talked about for the best fix, however if your unable to spend time and money try the gaskets. Make sure you tq the bolts in the right way, like you would a tire.

Good luck, I hate to tell you to step up to hedders but that might be a step down LOL.