I have a 3614395 N1 here that will fit the 1978 360 smog heads but you have to grind a little relief just below the lower rear smog port of the head on the driver's side to get it to fully clear. Not a big deal, get your clearance before you bolt it up with out the gasket. Smog ports get plugged anyway.
Also the same fits the non smog 360 J Heads better. Just double check if there are any Casting Lips sticking up, take a die grinder and get them out of the way.
I would think you can clearance grind for your 360 head just a bit to fit your original 273 manifold. then your exhaust pipe will bolt up the way it came out.
Same thing with the different casting numbers, just clearance fit your heads a bit to make them work. They are not far off, but they need the clearance so the exhaust gaskets will seal properly.