340/mag360 exhaust manifolds

Ok, thanks Treblig, I should have clarified what I meant, so the manifold I have that works is part # 2843953 and it is a dead center dump with a 1 3/4" inside diameter date code stamped 1969, the truck manifold I have looks exactly like picture #3 you posted part# 4041466 and has the same dead center dump as yours with a 1 7/8" inside diameter, the manifold I would need looks exactly like the manifold you have pictured in the top left corner sitting on some plywood that you posted 12/30/14 just above, the reason I need this is because it is very thin at each end, if you compare the two you have you will see what I mean, in my application the cab of the truck sits very far forward on the frame so the rear of the manifold is inside the stock firewall causing clearance issues, ( I may be able to use headers to solve this but still would have to locate the right ones), also, again because of this being a truck and street rod application I HAVE to use center dumps on BOTH sides, I guess what I was hopeing here is that the one you have pictured in the top left of the plywood picture would have a larger inside diameter, OR maybe you could tell me if I could machine the one I have?, also, fyi, I can use the 80 truck manifold on the passenger side, not as many clearance issues, and lastly the engine I am using is a 1969 318 from a Dart, thanks for your help


The 2843953 casting number you are currently using is a standard 318 late 60s manifold, I had the same one on my 69 Barracuda when I purchased it, it should look like the bottom manifold in the first pic I just posted (1 5/8" exit hole). The manifold pictured in the 12/30 post is a 70s 340 center dump manifold and that style of manifold are all 1 7/8", I am currently sold out of these. Mopar did make a large hole (2 1/4") center dump 340 passenger manifold but they cost a small fortune...$300-$450 (bottom manifold in last pic).

Unfortunately you still didn't tell me what size you mean by "larger diameter"...but I will assume you mean 2 1/4" exit hole. If you're looking for performance you could easily grind or machine down the rear surface of a 360 mag or Dakota manifold since they are super thick (1 1/2" thick) and would not break or crack BUT they are not center dump!! Then you also have the option of using the LARGE HOLE 340 driver's manifold which has the 2 1/4" exit hole (see second pic) and is exactly the same shape as the 2843953 you are currently using . Then there's the late 60s 340 large hole (2 1/4") manifold that also has the same shape (design) but is a little sleeker (third pic) and less bulky (no ribs, more clearance). But again, it depends on whether you're looking for good flow and performance or just a manifold that will work.
Hope I'm helping you here??? Wish you could post a pic of your engine compartment in the exhaust/firewall area???
treblig