Last time I Checked, Tj & Yj's were the same track width... but who knows maybe they changed within the last month
as far moving the passenger side perch inward, NO it wont off center anything... the drivers side perch is cut into the 3rd member housing...
its not like your moving both perches to the left or right.. your only moving one, because the F250 frame is wider than the Yj's
if you want to narrow them, but yet have a little more width, have them narrowed to Old Bronco Specs... from 67-72... they are 1.5" wider than Yj or Tj's... on the front only cut the long side down, on the rear... well you'll have to cut both sides
the longer the shaft the less likely you'll have to break it, thats the main reason alot of guys are staying full width... because they are CHEAPER!... plain & simple
but thats totally up to you
the front will be Lo pinion & so will the rear... on both axles
if for no other reason, buy them anyways, if you dont feel like running them, turn around & sell them, but add a couple hundred to the price, you can easily sell them for 500-600 bucks
but for the same price you'd pay for those axles you could easily buy a set of 2.5 ton rockwells & throw detroits in them & still narrow them.. cheaper, plus have a hell of a low gear... only draw back,42's would be the smallest tire you could run.... but then again 42's aint such a bad idea anyways.....