For what it's worth... I have done this conversion before. If it is anything like mine the 4x4 motor mounts/crossmember will not fit due to different frame C section height. The easiest way to do the swap is to take the front spring hanger brackets off of the donor truck all in 1pc, ie there are 3 separate brackets (core support mount, spring hanger, and an "L" support bracket) that are riveted to the frame that create the front spring hanger bracket assembly. It is important that you only take the rivets off that hold these 3 brackets to the frame and leave the rivets that hold them together to each other intact. Knock off the core support body mount bracket on the 2WD truck. Put the 3pc bracket assembly that was removed from the 4WD truck up to the frame. Only 2 of the 4 rivet holes should line up. Put some bolts in the 2 holes that line up and redrill the other 2 so that they lineup as well (note-you may have to weld up the 2 that don't line up and grind it flat before redrilling). Once these are bolted up you can put some clamps on the remainder of the bracket and drill the holes into the 2WD frame using the holes in the brackets where the rivets used to be on the 4WD frame. For the rear shackle mount, I basically cut a section out of the vertical side of the donor frame that included the shackle hole, the 4 bolt holes for the shackle mount bracket, and the forward 2 rivet holes in the front cab body mount bracket. This will become the template to make the holes for the shackle mount in the 2WD frame. Once I had the template section cut out of the 4WD frame I knocked out the front 2 rivets out of the front cab body mount bracket on the 2WD truck and then you can bolt the template from the 4WD frame to the 2WD frame using the 2 now empty rivet holes in the body mount bracket. This will ensure that the shackle bracket is in the correct location. Once the template is bolted to the frame you can use it to drill the 4 holes for the shackle mount. Put some bolts in these and you can actually use the clearance hole as a guide for a hole saw. I don't remember the exact size but I think it was around a 1 7/8" or 2" holesaw and it pilots perfect in the template. Once you have these brackets complete the rest is easy. Take the 2WD suspension crossmember and cut it flush with the outside frame rails (basically cutoff the areas that have the mounts for the A-arms and spring pockets) and reinstall into the 2WD frame. You may need to trim the height of the 2WD crossmember if you are not planning to lift the truck any. The one nice thing about using the 2WD crossmember is that it bolts in from the bottom of the truck so if you ever need to change the oil pump or pan gasket or bearings it is as easy as unbolting the crossmember and taking the pan off. I wish I would have taken some pics when I did mine.
