My 440 1970 six pack Challenger [original V code car] came with 2806900 manifold on the right side and 2951865 on the left side. Had aftermarket exhaust on it. Parts book says it should have 2899879 manifold instead of 2806900.
Looking at pictures 2806900 and 2899879 look identical except for heat riser valve placement. I plan on putting OEM exhaust on the car but not sure if it will work with the 2806900 manifold? Does anyone know if the OEM pipes will bolt right up? Thanks in advance!!

I bought the correct number exhaust manifolds for my '70 Bee, same numbers as you quoted(879 and 865), and purchased a 2-1/2" system from TTI. The system fit nicely and sounds awesome. How correct do you want to be? TTI requires manifold numbers when you order. And '70 B and E used the same manifolds.

http://www.mymopar.com/extcastnumb.htm

The 2806900 manifold is '68-'69 and has the stamped steel counterweight, the '70-'71 manifold has the cast weight. The bolt holes are also clocked differently. Proper or correct headpipe won't bolt up.

Thanks! That's the info I needed!