There is a thread on the oregon 76 chain in the bar chain area here. I had a lot of NOS 76 chain and stihl chain in same type stuff. I tried the 76 on a new 550 with 20". Still wasnt happy. Just to long of bar for 50cc.
IIRC there was also McCulloch branded Oregon 76 for a time as well. Do you still have that NOS 76 chain Kevin?