Back to your original question, you can measure the distance between bolt-holes on the flange to figure out the size (small or large, I think the large is 3" between bolt holes). I think with the conversion part numbers I posted you can choose the size of your U-joint (1330 or 1350). Most of the driveshaft folks have a little measurement sheet with directions and you send that in to them, it would include the type of connections and they would make the driveshaft from that. Bunch of Explorer 8.8 info at Ford Ranger forum:
http://www.therangerstation.com/tech_library/Explorer8_8.html Did the shop center the pinion by cutting the long axle tube 3" and using a stock short axle on both sides? That seems to be the easiest/cheapest way and no custom axle costs. Since I am putting Fatman's on the front I am going to run Ford pattern wheels and I can use stock over-the-counter parts as much as possible.
For harness I am planning to use stock harness with stock fuse underhood box. See
http://www.lt1swap.com/underhoodfuseblock.htm I have the fuse box --Ebay for $30, came with all relays and fuses which in themselves were probably worth more than that. I am planning to hook up power and ground to that box (using stock battery cables from stock harness), then run fuel pump relay, tach signal, ignition, etc. as show in the link. Trying to keep everything as stock as possible to get running, then modify things as needed. I think I will have to figure out how to wire in a OBDII port and an engine check light, but other than that, I should be able to take to local Chevy dealer and tell them to act like it is a 2003 Silverado.
PowerTV folks have been sending harnesses to 150tunes in Spokane Valley, WA. and they are about cheap enough that I may go that route.