I can setup a suspension that won't blow the tires off with a 502, but its not gonna be cheap.
You can get a set of 15" wide tires to break free if the suspension bounces around everywhere.
I'm a little rusty on the 60-62 as you guys had the x-frame, making some interchanges a tad different. But I"m pretty sure this all still applies. Normally for the 63-66 crowd, I recommend going to the 67-72 or 73-87 stuff and swapping to 5lug. It makes wheels easier to get, the parts are readily available and not too expensive. I usually would take the rear axle as well.
We used to have a better FAQ, the new one throw me off....but check out some of the threads on disc brake upgrades, as they explain most of the stuff.
http://67-72chevytrucks.com/vboard/s...d.php?t=263983
Going to trailing arm rear suspension isn't terribly difficult either, and its pretty darn effective. The trailing arm rear is whats on my '66, and allow me to fit the tire I mentioned above.
IMO, don't get hung up on how big your tires are. You get to a point of diminishing returns on the street, and you might actually
slow your track times down with too much tire.