318 low budget heads change
You'd be best off with the 302 castings on a 318. The 360 heads on a 318 drop compression and don't offer much added flow that the 318 can take advantage of. The J heads are nice for the big valves and such, but again, you wouldn't see a big advantage with the 318. The heart combustion chambers on the 302 castings are the way to go for a 318.
As Mr. Don-Vee stated,,,,,,,,,
The Casting #302 Cylinder Heads are the easiest choice, as they will bump-up Compression and
will add to the needed Horsepower in the 1972 '318'.
The #302 Casting is a good general purpose 'low-to-mid' Performance Cylinder Head,
which relates to 'functionability'.
But, these Heads have a tendency to 'crack', and usually where you can't see it visually,
under the Valve Seat or between the Valve Seats.
I would never put a set on any Engine without having them pressure tested on an 'AXE' Cylinder
Head Pressure Testing Unit first.
Probably $50 to have the set of Heads 'Pressure Tested'.
Sounds like you want a 'Low-Budget Upgrade', and it wouldn't cost that much for a
basic 'standard' or 2-Angle Valve Job.
If the Cylinder Head Surface is 'square' {flat and not warped at all}, you can get away without
Milling them, and utilize a Thin Cylinder Head Gasket..........
Does that sound like the direction you want to go in........