Im not exactly sure on how thatll affect you, but just a bit of related info... Magnum heads will bolt on to an LA block as long as you equip it with lifters and pushrods with the oiling provisions in them... LA heads are oiled from a passage in the block, magnums are oiled from the pushrods... If you want to use a magnum block with LA heads erm, well thats a whole lot of work, unless you fall on an early magnum block (like mine) that still has the oiling provisions in the block. Also magnum and LA intakes wont interchange without some machining....
I know I havent answered your question, just FYI

 

The heads will fit on a 360. Im not sure how much compression you will gain, but with the 2.02 inch valves machined into the 318 head you will.have a good combination. 360 heads on a 318 will lower compression unless you shave them down and then you might have to get your intake shaved as well.

 

I have 96 dodge stratus #2&4 has no fire