Replace fan belt on ford 4500TBL

I have a 3500TLB with the same arrangement. As Buddy said, it can be done. I don't think I could get at mine from the bottom, though. The back support (I don't know what else to call it)for the front axle would be in the way. I took the hood off and reached down from the left (sitting in the seat) side. The hardest part was getting the four bolts that hold the u-joint (yours does have a u-joint, right?) to the pulley loose. I could only get a wrench on two at a time, the one on top and the side closest to me. Once I got them loose enough to turn by hand I had to turn the engine half a turn to get the others. Not hard to turn, in fact I remember now needing to put it in gear to break the bolts loose without having it turn. (Think safety, do all this with the kill switch pulled.)
After the bolts were out I was able to work the belt through by wiggling the u-joint back and forth and working the belt through the (waddaya call that yoke thing) one wing at a time.
I still carry a cut-to-length belt in the tool box in case I pop one in the woods.
Wm
PS If yours has some other shaft arrangement, I take it all back.

I took the old belt to the Auto parts house and got 2 belts I thought were about the right size, then returned the one I did not use.

I had to remove the bolts for the hyd. pump and pry it just far enough out of the way to work the belt between were the shaft splines slipped apart. I did not remove any hyd. lines or hoses, there was just enough flex to get stuff worked apart. Then was able to get everything put back together.

Good luck!
MrBill