302 heads...were to buy..what works with..?

Your stock heads will easilly support your goal. A 350hp 318 basically has pistons to get the static up to 9.5:1, a performance valve job, a decent intake, and a modern cam, a 650cfm carb, and cheap headers. I would upgrrade the valves to 360 size (cheap to do) and have the intake ports gasket mached to the 340/360 port size to make the intake selection a lot better. IMO, if you want to spend on heads, the EQ manumgs are a great head for a 318 and reasonable price. They would be cheaper to buy for me than paying to completely prep a set of 318 or "302" casting heads.