all f250 blocks are 2" and all F350 blocks are 3 7/8" (roughly).
Or at least I haven't heard of any years being different.
They'd work either way as axles all have a hole in the perch and a pin on the top of the block.
For me it was cheaper to buy new fabbed blocks from omf than ford. Ford is very proud of those blocks. So hopefully someone will trade you.
I wound up ordering a 3.5" block with 2.5° of taper and my truck sits just right with a 3" pack in the front. My 35s dont fill the wheel well but they fit nicely.
For oem, the blocks have taper or not depending on the wheelbase? I need blocks for my cclb 95 with 06 axles.