360 Heads on my 318?

a couple things..

If you want to run the small valve 360 heads, you're gonna wanna cc'em and most likely mill them down [to about 60 cc's] which is no problem really, unless you can't afford $75 for the cc kit off of ebay.

the runners in 360 head are a lil big and would be mostly beneficial above 2500 rpm, which is no big if you have 3.55+ gears and a cam 256+* duration.
The thing that is hurt you in this is that 750 carb, even with the heads, it is too big to help the bottom end.

I think with a 600 cfm carb, high initial timing [20-26*] , milled 360 '60-63 cc' 360 heads and that small runner performer intake, the 318 w/360 heads would work fine and make a lot more mid range and top end than any 318 head in stock form.

it all about compensating with careful parts selection and GOOD TUNE.

I will add...if the heads need building...consider the rest of the motors condition, cause you might find it better off to do a full build and a 360 instead