Need advice on my 318

An update for Treyblig... Just 30 min ago I found a guy who has the 273 66 dart manifold near my home...its a ***** to find but for $65 I can pass it up. If you still want to see if your 360 header fits I don't mind checking, but can't buy it since I'll already have what I was after. I know the 360 flows better, but to get a 100% figment guarantee is Valueable. On the same note, does it make any sense to use the 273 manifold in one side and a 360 on the other? What happens if one side of your exhaust flows better?