Can anyone tell me what engine/car originally used these exhaust manifolds? They were on the 455 I bought in 1999 to put in my 1979 Hurst/Olds. I replaced them with a pair of W and Z manifolds since I didn't want to use headers at the time. I threw these in a box and they've been there ever since then. Any ideas? The first is an X manifold 406301 with a date of 8. The second is a T manifold 398708 with a date of 351.

 

pictures

 

Having an issue with the pictures... or just could be the operator...

 

406301 is a LH manifold from a 1971-72 Olds full size with a 455. 398708 is a 1968 BBO RH manifold. Neither of these is internally divided like the W/Z manifolds and thus will not flow as well. They were not paired up on an engine from the factory, either.

 

Thanks.
The 406301 LH manifold makes sense since the motor came out of a 1971 Delta 88. Guessing the owner of the car/engine before me changed the RH for some unknown reason.