I have a 68 firebird 400 and my LH exhaust manifold cracked i found one on craigslist cast# 490144 but when i look it up it shows that its for a 1969 firebird my question is does it matter? can i still get it and make sure itll fit my bird? heres a picture itll do until i get some new headers. Its only $50

Sub frames are the same. Same steering box.same engine. I think you'll be fine. I'd try and get the price down to $30. Fifty seems like a lot for one side.