Cheap and simple is to advance your timing 3-5 degrees, add a free flowing airfilter (K&N etc) but probably your best bet would be to swap the intake manifold with a better one. There arent too many options for a tbi manifold but Edelbrock makes a decent one. Match that up with a decent pair of headers/exhaust and you should see ~15% hp gain with little effect of fuel economy. All of those can be transferred over to a 350 if you upgrade later. It may not be worth it to you to swap camshafts but another increase can be made there. The 305 suffers from a very small bore diameter, so large valve heads arent really an effective option (price wise either). Stick with the small stuff and build your 350 the way you want it.
