Incline Question

Hi, I'm thinking of putting an engine on one of my bikes by this summer. I have to make a trip to my parents and grandmothers house about once a day and my truck has a mildly built v8 in it, with the gas prices I thought this would be a good way to cut some costs. The issue is that I live in East Tennessee where we have a lot of hills some that can be fairly steep. I need a kit that can climb pretty well. What kit or tips would you guys suggest. The bikes that I have to work with are 2 mountain bike 26" on Mongoose with full suspension, the other is a huffy w/o suspension. I do have a 20" bmx and an old Azuki road bike 27" if i can find good tires for it.