The original GM F-41 shocks haven't been available from GM for decades, and the part numbers in the GM parts book are different than the part number stamped on the original production shocks; the service part numbers are different, as they describe the shock, a hardware kit, and a box.
The NCRS judging guide has the part number stamped on the shock (and the dating convention) - that's the number you're looking for. You'll have to keep your eyes open for them on eBay or in the NCRS "Driveline" classifieds; they're very expensive.