ok, now that you've settled on building a "classic", let's make sure you do it right. It would be quite irresponsible for myself, and others on this board to not address the most important part of hopping up any car, but especially old Stangs.......Suspension and BRAKES.
I know it's not glamorous, and it's hard to brag to your buddies about putting in new strut rod bushings or ball joints, but it is are absolutely essential that the car handle and stop well and to do it consistantly. You really need disc brakes up front.......four wheel discs are great, but you really just need to make sure the rear drums are in good operating condition.
It's easy to get going fast, and it can happen in a big hurry once you get into the 250+ hp range, and you need to know that the car can slow down and make that emergency lane change when somebody in front of you does something unexpected. Please don't overlook this part, we would all hate to see something happen to you.
Now for the fun stuff......MORE POWER. God wouldn't have given us gobs of tire-frying torque and horse power unless he intended us to use it.
My advice.....put in a 5.0 (roller cams are wonderful inventions), stick a five speed behind it, buy some 3.80 gears(closest thing to 3.73's you'll find for that 8" rear), top with fresh basil and garlic, bake for 45 minutes at 400 degrees and ....ooops, wrong recipe......put a dual plane intake and 600 cfm carb on top, use 1 5/8" headers and enjoy. Yes you will go through tires quickly, but you just have to budget for that.
Best advice about driving fast.....learn when and where to do it. It doesn't belong everywhere, and the cops will surely remind you of that fact. Don't get me wrong, I drive my car on the street every day, sometimes much faster than I should, but I will NEVER drive stupid on a residential street, and I won't open it up unless I have a good open road without traffic.
To quote the great Peter Parker aka Spider Man "With great power comes great responsibility."