Cylinder head choice

Well, if this is going on a stock 318 bottom end, Xs & Js will kill what little compression you have, as stated above. 302s are a possibility if you can find a good pair, but without any additional work I don't see a substantial gain to be had over your stock heads.
For your tentative $550 budget, getting your stock heads (you already own them- $0 outlay) freshened- seats, guides and cut for seals; good springs for your application and retainers/keepers will eat all of that up (and then some). If the budget allows, you could always have a set of 1.88 intakes (guys upgrading their 360s to 2.02s may allow you to score a set on the cheap) thrown in them while they're at the shop- and if you're up to the task, do a little port smoothing/matching, and the stock heads can do pretty well on a mild teener.