If you want to play around with your 302 now, do it budget, gt40ps, exploder intake and tb, etc. etc. You can give yourself another 100 horse for less than a grand and have some fun.
For the "real" build it really depends on what you're looking for. If you want more than 400rwhp not running on borrowed time you really should look into a 351-based build. If only because it's a gamble to make that much aon a 302 to the rear. Some crack right away, some don't, but you don't know. You'll have much better chances with the 351. You can even leave the rotating assembly alone, still have more than 347 cubes, and all the other upgrades are just like a 302.