I'm going with a 440 in the 70 challenger, so I need to get the exhaust castings to match the rest of the exhaust, I'm not concerned about them being "70" casting numbers
I found out the 1970 RH casting is 2899879. (The LH casting as 2951865; I have one of those)
The RH 2899879 is B/E for 70-71. Books also show 3751071 correct for "B" cars for 73-74. (no E's had 383/440s after 71) I have a 3751071.
Now the question is: is the RH 2899879 the same as RH 3751071? if so....I'm set.