Alternator pulley size

[eqdt55]

Does anyone know the standard pulley diameter for 1994 6.5l 105 amp alternator? Should I even be worried about getting right size? 4.10 gears auto trans. At 55mph tach showing 2475 rpm.

[grancito]

It is 2 1/2 inches where the belt runs, a different size will make the tachometer read wrong.