I did the 400at diff swap on my 350 rancher and it works super good!!! I used the 400 front diff, drive shaft and the 2wd/4wd switch from the 400, I changed the top cap in order to get rid of the auto/ESP switch. This is a direct fit, the only mod that has to be done a small V needs to be cut out of the 350 frame in order for the bigger diff to fit (you will see when you set the diff in place) the 400 has this cut out from the factory so it will not weaken anything! everything bolts right up no trouble at all! The wiring is just as easy also, you will only need two wires on the front diff. the orange and the white that switches it on and off, it will be the only two wire plug on the diff, cut the 2 three wire plugs off and toss them, there is only two wires on the diff now, orange is + white is - hook the white wire to ground and the orange wire to either wire to the 2wd/4wd switch then hook 12v from the key switch to the 2nd wire on the 2wd/4wd switch. that's it you are done. REMEMBER TO ONLY SWITCH 2WD/4WD WHEN YOU ARE AT A COMPLEAT STOP!!! works 100%!!! As of right now you can get everything you need on ebay for about $120 after the word gets out that this is a direct bold on the price will go out the roof!! if you need more info just ask. God bless