Miss-matched heads & manifolds?

Hello there, just picked up a 64 Valiant with a mid 80's 318 in it. I've been trying to track down a exhaust leak from both sides. I thought maybe the exhaust manifold gaskets were leaking or maybe a head gasket. Some quick info for you, the seller said he a had some 360 police heads put on a couple of years ago on this 318. I have not verified that yet. Any way it's using 273 exhaust manifolds and I realize that they are not big enough to cover the ports on the heads! It looks like they filled the bottom of the ports below the exhaust manifolds with JB weld or something. I can look it up but I'm trying to save time here do I need to get different 360 exhaust manifolds to match up? Are the old 273 manifolds to small? How about 318 manifolds will they work on 360 police heads? A lot of questions, I have to run now but I will check back later.