As Woody eluded to, there is ZERO benefit to actually buying bigger calipers. If you keep everything else the same and put a caliper with a bigger bore on it, you're actually increasing your pedal travel...and your stopping distance will worsen. I did a full writeup on this subject on GMC4x4 with brake distances measured.
To fully realize the benefits of 3/4t calipers, you must upgrade to hydroboost b/c as Woody said, it's all about PSI. As an example, a stock vacuum system generates about 800psi at the caliper and hydroboost generates 1200psi. If you swap up to 3/4t or worse, 1t calipers on a vacuum system, you're going to create <800psi at the caliper for a given amount of pedal travel.
If you already have hydroboost and you'd like to purchase larger calopers, you will still see WORSE results then keeping the stock ones on. To realize the benefit of these larger calipers, you will have to pair this to the appropriate sized hydroboost and PS pump...and yes, there are different PS pumps and hydroboost units for the various caliper sizes.
I hope this helps!