This might be helpful.
When I installed an 8BA in my 40, I used 8RT water pumps and 8RT wide belt crank pulley and wide belt alternator pulley. One long crankshaft pulley belt turns the water pumps and alternator. The other short belt runs between the crank pulley and the fan pulley. Had to buy new belts that would fit.
The new shorter belt is a wide fractional Horspower Belt. You can see the numbers on the belts. Fan hub pulley is homemade but, your original will work too.