You might want to hold off ordering a new exhaust manifold until you can remove yours and inspect the port alignment across the top. They must be in perfect alignment. Often the back port droops as much as 1/8", which will lead to gasket blowouts and ticking exhaust leak sounds. Generally, those aftermarket heater manifolds like yours are more robust than the Ford manifolds and don't have the tendency to droop like Ford manifolds. I have yet to come across an aftermarket heater exhaust manifold like yours that does droop in the rear. It seems like 9 out of 10 Ford manifolds I see on driver Model A's do droop because gland rings had not been installed by a previous owner so that the weight of the muffler pulling down on the back of the manifold causes it to droop in the rear after hundreds or thousands of heating-cooling cycles. Yours might be a case where someone neglected to install gland rings in the exhaust manifold and only blew out the gasket while the manifold ports themselves are still lined up properly. No gasket made of any material will last long without those gland rings in place. Ford eliminated them for a short time in 1929 to save a buck, but customer and dealer complaints of blown gaskets made him decide to return to installing the glands. You might get lucky and discover your exhaust manifold ports are still in alignment across their tops.
To test for this, lay a METAL straight edge (not a wooden paint stir stick or a wooden ruler) across the tops of the ports, aligning 1, 2 and 3 first. Then see if #4's top port also aligns with the other three. If it is below the straight edge, chances are the rear of the manifold is drooping and consequently the glands cannot be installed.
In my experience, the only gaskets worth using behind the exhaust manifold are the copper ones. The cardboard gaskets blow out real soon, even with the glands in place. They are not made like the ones available years ago. You might as well use toilet paper. I also have had no luck with the long one-piece shiny silver gasket. I could never get even a straight manifold to seal satisfactorily with that gasket. The copper gaskets are more expensive, of course, but well worth the money.
If you are concerned about future distributor removal with your heater exhaust manifold in place, why not mark the place where the lock bolt is directly across from the manifold and drill a hole through manifold so that you can put a flat blade screwdriver through the manifold to loosen the bolt? You can reach the nut between the manifold and engine block with a 9/16" wrench to loosen it slightly, so you only need to be able to access the slot in the bolt through the manifold. The hole need only be big enough for the screwdriver blade to be inserted through the top of the manifold. Exhaust fumes will not escape through this hole because the exhaust area of the manifold is separate from the top where the heat goes through. The rear moving air through the radiator will push the heat past the hole at a speed where you will not be losing heating efficiency. You could also tap a thread in the manifold hole on the outside of the manifold and plug it until you need to remove the distributor again. But how often will you need to do that once it's been rebuilt? Only the changing the condenser would require distributor removal. Changing the points can be done without distributor removal.
Marshall
