c body exhaust manifolds on a 400 in our duster

They both came on a 70 383, the guy I bought the engine from said he pulled the engine out of the car in the mid 80's along with the transmission. Said he bought it from the original owner that had parked the car in the mid 70's in a field. The transmission is in the duster, along with the '76 400. The 383 I bought complete with the exhaust manifolds. It's in the tractor shed waiting for the next build. Given the cost of Schumacher headers, unless it becomes an issue I'll be staying with these manifolds for awhile. I'll get the numbers off of them and see what they come back as.