360 heads on a 318 of any benefit?
The 360 heads can flow more due to larger valves. They also have larger runners,.
While this is true, the 318 gobbles down air and fuel at a much lower rate. The potentail flow of the 360 head is not fully realized on a 318 until much much later in the rpm band. Until you get to the area where the engine can make use of the air flow ability of the larger port, the air moves slowly in the intake and head track. This drops fuel out of suspension and creates big droplets of fuel that will not burn so well once in the combustion chanber.
so the stock 318 stuff will create bad flow characteristics in the runners.
This is simply not true of the heads. This is a mistake. It should read 360 instead of 318. I'm going to assume this is a typo. The smaller 318 head port will keep velocity up instead of droping it. Velocity is the key to makeing HP in any engine. The 318 suffers greatly from a lack of it.
Between the smaller bore and shorter stroke, the engine needs a smaller port so it can draw on the air and fuel well and really, the small port is an ideal set up.
Aftermarket intakes, and a stock 360 intake will work and will avoid this problem. The other issue could be compression ratio. Much of this depends on the configuration of your engine. If its stock, it may lower the CR a bit.
On the cheap, a 360 head , intake and a T-Q are the best hop up parts for a 318.
However, if you want to do better and take some time and money spent well and not just spent......
Add a 1.60 valve to the 318 head, port the stock 318 head and back cut the valves. Add the Edel. Performer intake. The head and intake's ports should match. Carb of your choice. I like the T-Q for a dual performance carb, but add what ever carb you like.