Toss them in, set them up evenly and drill a few 1/8" holes to screw them together where they overlap. Take them out of the car and support them and take a good metal blade on a sawsall and using a chalk line mark, cut through the both of them which will give you your width AND the gap to weld them back together again. it's a PITA and by the time you grind and finish the welds, you'll have invested enough time to have bought the one piece. Good luck