Make sure the truck is completely level side to side and front to rear. Mark the centerline of the original suspension before you remove it. Find a common spot on the cab or original frame from which you can measure diagonally toward the front as well as straight to be sure the subframe is perfectly square. Plan on lots of gusseting to ensure a good graft and if you can overlap the frames where they meet that will make the joint stronger. Use tack welds here and there and keep measuring after you tack it in to be sure it didn't move. Keep moving from side to side as you weld it in instead of staying in one place...that's all I can think of right now. Good luck...
