Are these 340 exhaust manifolds

I just picked up a rebuilt 318 for the 73 Duster my daughter and I are building and the previous owner said the exhuast manifolds are from a 340. The driver's side is 2.25 ID but the pass. side is only 1.875. Here are the casting numbers as best as I can read them
driver - 3614368-1
pass - 3418623

Can anyone tell me what these are for sure?

Thanks,
Ken