1969 L78 837 alternator pulley

[Firstgenz28s]

Good day SYC members. Can anyone provide me with correct diameter for the alternator deep groove pulley?
Much appreciated!

[Mr70]

It's Alternator Pulley #1970831 has an outside Dia.3-3/16" and a shaft Dia of 11/16" with a 1/2" Deep belt groove.
No identifying numbers were stamped into this pulley.
Was used on:
1969-70 Chevelle w/solid lifter 396,454
1969 Impala series w/solid lifter 427
1969-70 Nova w/solid lifter 396
1969 Camaro w/solid lifter 302,396,427~COPO
1970 Camaro/Nova w/LT-1 350

[Firstgenz28s]

Thank you!

[rszmjt]

It's Alternator Pulley #1970831 has an outside Dia.3-3/16" and a shaft Dia of 11/16" with a 1/2" Deep belt groove.
No identifying numbers were stamped into this pulley.
Was used on:
1969-70 Chevelle w/solid lifter 396,454
1969 Impala series w/solid lifter 427
1969-70 Nova w/solid lifter 396
1969 Camaro w/solid lifter 302,396,427~COPO
1970 Camaro/Nova w/LT-1 350

FWIW - Actually a lot of production line installed Z28 alternator pulleys have “3” small slashes on the front face of the pulley, very hard to see.