headers

Hi
I'm not a MoPar expert, but I have a 74 duster right now.
I picked up a pair of headers from a guy I know, he said they are
for a 318. so my question to all of you, are headers for
MoPars like a universal fit, or specific to each model.
I know on Fords from that period its model spacific.
I have not seen a name or any model number on them...
Best