Another thing, back in those days cars werent really built for the kinds of speeds cars see today. 55mph speed limits and the such meant you didnt really need tall tires or overdrive trannies where as today (in Southern California anyway) the freeways fly @ 70+ mph, and the cars are built accordingly. Are 13s a problem though? Not really because its all a give and take. It all depends what you want out of your car. A buddy of mine has a lowered Valiant wagon with 13s and it looks good and does ok on the fwy thanks to a good running little slant and the right gears in the rear end. Does it accelerate like a super stocker? Nope, and he doesnt need it to. Does it keep a 65-70 pace on the feeeway without breaking a sweat? Yep. So really, wheel diameter is more of an aesthetic thing so I say run em if you like em.
