I have a 77 super le tour that I’ve been fixing up, it’s pretty much done and rideable (rides like nothing I’ve ever been in btw) but now I want to put a new chain in it what kind and size do you recommend? (Brand and dimensions that is) and does anyone know of a lightweight guard for the front sprockets, I’ve got two pair of jeans now with rips on the right leg from the sprocket lol
Bicycle chains are heavily standardized. They all use the same 1/2 inch pitch. All derailleur systems use chains with 2.4 mm internal spacing between the plates.
As manufacturers increased the number of sprockets in the rear cluster the sprockets had to be spaced closer together, which necessitated use of chains with an correspondingly narrower outside profile. You'll see that chains are specified for '6/7/8 speed', '9 speed', '10 speed' etc. 'Speed' here means number of sprockets in the rear cluster.
A 1977 bike presumably has 5 sprockets in the rear. Any chain good for a 6 speed will work.
Chains come with more links than you need and are cut down to size and joined. Instructions on how to do this are easy to find on the internet.