Drive belts??

[mowerman1193 32]

I swapped a 14hp motor from a Bronco 14 and put it onto a C-121 Auto. I used all the parts from the C-121 other than the motor mount cradle as I bolted the 14hp directly to the frame..The drive belt from the motor to the hydro pump calls for a 5/8" x 82".. Picked one up but it is not going to go on..Does mounting the engine change the belts length? just wondering if anyone knows what belt I might need?

Thanks,

Kevin