On most of the 77s and 88s I grew up with the front wheels had a large cast iron hub. The open rims were attached with 5 bolts around the outside. The 77 I have has a smaller hub that has 6 bolts and uses a closed pressed steel rim.

Does anyone know when that change was made or if they were sold each way as an option?

Just as a matter of fact, the front axel on mine was taken off a junk 88 after the cast iron section of the original front axel on the 77 broke for the second time. I don’t know what year that 88 was made.