1965 PosiTraction Lubricant Recommendation

[48Super]

I'm looking for some advice on what is the correct lubricant for a PosiTraction rear in a 65 GS. I've read a lot of conflicting information. Is it sufficient to use the newer gear lubes which are formulated for both conventional and limited slip applications? Is is recommended to also use the special GM additive in addition to gear lube? I'm not currently getting any chatter or other problems with the differential, I just want to add fresh lubricant because I believe it has been a long time since the last refill. Thanks for your assistance.