What to do, what to do? Rear lift question

[Critter]

Here's the background, I just got the 78 in my signature and plan to have a little fun with it but do it on a pretty low budget. As my sig says, its a 78 K20, 454 4-speed. I will need to pull a bumper-pull trailer from time to time and possibly even a gooseneck here and there (it already has a hitch in the bed). My plan is a 4 inch lift with 33 inch all terrain tires. In the front, obviously will be new lift spring, but what do I do with the back? I can't get a straight answer from anyone as to whether or not aftermarket rear lift springs can be bought in a 3/4 ton capacity or if they are all basically 1/2 tons. So vote and let me know, keeping in mind frugalness, the fact that I want to keep my 3/4 ton capacity, and some trailer pulling from time to time...lets say no more than 6000 lbs.