Frame modifacations?

i have a 1988 chevy k1500 4x4 thats in pretty rough shape, ive been in nc for a few years and i just got back to ny and pulled my truck out of the barn and im seeing all the damage id done to the frame when i was younger and now i NEED to do something b4 the truck is completely jumk. I just bought a 1990 k1500 4x4 that has a very sold frame and i want to do a frame swap, But b4 i do i want to do any and all modifacations to the frame that i can b4 i put the body and the new motor in it. I plan on undercoating everything under the truck when its all apart. i want to box the frame?but im told i need to find out a little bit more b4 i do. i want to ass supports to the frame but where? im moving the fuel tank to in the bed. i want to make one hell of a trail truck so any help would be gratly appriciated. im getting my new donor truck on 12/16 and then the project is begining

[scabbyota]

When I was a teenager working in my dads shop we would make frames stronger by fish plating.We would take 1/4 to 3/8 flat metal and slab it to the solid side of the frame with 1/2 high strength bolts.No welding.I've never done any boxing in but it sounds like a good idea.I was taught to never weld on a frame unless necessary like cracks and stuff.If you do box in I would'nt weld one solid bead I would probably weld 6 inches and skip 6 inches.That would allow some flex and if a crack did start in the weld it would stop in skip spot.I'm sure there are others with more experience then me who can help you.Good luck. [img]/ubbthreads/images/graemlins/thumbsup.gif[/img]