I wouldn't mess with the engine just yet. You would have to drop AT LEAST $750 (cam kit, intake manifold, carb, headers) in that thing before you'd start to notice a lot. You still wouldn't gain a whole lot by just doing that, either. The real bottleneck in our Windsor engines is the heads. Cylinder heads are not cheap. You're looking at over a grand just for an assembled set of aluminum heads, not to mention all the other parts you'd need along with them for the install.
If I was you I'd start with the rear end. I'm guessing you have an 8" open rear axle with some crappy gears like 3.00:1. That's what my '69 coupe had in it with a 302/auto from the factory. Do you know what gears you have?
You could stick with the 8" and upgrade to some steeper gears and a posi unit, but I wouldn't. I'd try to find a 9" rear with posi and determine what gears are in it. If they aren't at least 3.70s, go with something steeper.
You'll be able to notice a lot of difference--especially in first gear--if you upgrade from 3.00:1 gears to 3.89s or 4.11s.
Just my opinion.....
