68 C10 5 lug axle question please.

[GMJimmy]

Please forgive me for asking a question that has probably been discussed several times on this forum but I don't have the time to search and read them all.

Question is my 68 SWB C10 has a 12 bolt rear end and has 5 lug axles (5X4-3/4") and they need to be replaced. I was under the impression that these trucks had 6 stud axles from the factory? If so, Is there a 5 lug axle from another year that you use for a conversion or do I need conversion axles? The ones that need replacement look like old GM axles.
Thanks for the help.
Jim