I have a 03 4x4 single cab silverado with a 4.3 vortec that finally gave out at 219k. So i get a motor from a salvage yard. Turns out it is an 05 4.3. Well i started unhooking everything to do the swap. I noticed the fuel lines are totally different. The 03 has a pressure and return line. The the 05 motor has 1 large 3/8 line only. Also on the bottom of the engine housing on the passenger side there is a wire connection that look like a nut. It is there on my 03 but the 05 motor there is nothing. You can tell it's the same casting but it was deleted. Kinda lost on where to go from here.