I agree that the later heads are identical. Also in the fact that you can get out cheap. Years ago with a 71 Ford I was in a similar bind with no cash
First, if it just needs a head gasket, why rebuild? Save yourself some cash and just get it hitting on all 8.
If it does need a rebuild. Even if it is a 360, you can see some noticeable increases from a stock rebuild, a set of inexpensive headeers and a good dual exhaust with a balance tube.
My next step would be 4 barrel, probably Edel 600 on a stock intake. You wont need much to get that thing making torque. Just get it running right