If you want to split hairs, there's 4 SBC pumps; early(short) late(long), 72-82 Corvette(short with extra heater hose nipple on the top)) and V8 Monza(short with threaded hole for P/S bracket on top). If you're in a pinch you can use any short pump but there can be pulley alignment and fan bolt pattern issues with the early short pump but the Vette one will work by eliminating the bracket. Another possibility is an aftermarket short pump; $60 in iron or $120 in aluminum from Summit.
Edit- There's more; late87&up with serpentine belt drive are reverse rotation.
77 Vega Estate wagon- project will have TPI305/T-5, S-10 spindles/axles
72 Vega HB Drag Car -383/'Glide/9"(firstname.lastname@example.org)(email@example.com 1/8th)
76 Vega GT- 400/4spd/9" retired from active duty(rusty)
04 Silverado 2WD ex.cab (work truck/parts hauler)
06 Haulin' 20ft enclosed car transporter
93 Suburban- 350/4L60(retired)
00 Saturn SW2- wife's car
01 Saturn SC2- younger son's project
00 Saturn SL2- daughter's car
98 Saturn SW2- older son's ride
99 Saturn SW2- spare
and 2 more Saturn "parts cars"
Note- the very act of listing all of these has made me realize I have some kind of problem.....