Hello and welcome to a great forum Matt,
I too pilot a '72. A '72 combat in yellow regalia.
Us '72 guys got to stick together we are a unique year
Got a great bike to ride once you get familar w/ her.
I have freshened up mine over 4 years and will field any '72 specific questions.
Also there are some really experienced Nortoneers here as well.
I use Castrol 40 wt straight and change it at the end of each riding season.
This has equated to approx. 600 miles a season.
It's cheap prevention. Castrol 40 wt is avail at most auto parts outlets.
Drain the sump as well, lil plug on bottom of engine case. I run an anti sump valve.
I know there are a million opinions on these. I start my bike and look for oil return
before I take off anyway just because.
Anti-sump worked last winter well. I went out to bike in April.
It had sat since the previous November.
The oil in the tank had dropped a mere bit.
I didn't have to drain out the sump at the start of riding season.
A shop manual is a must as these were do it yourself designed machines.
The Clymer book that covers Norton,BSA,Triumph in one manual I have found to be the easiest
read and keeps it simple. The factory manual is good but assumes you know what your doing.
And lastly remember the only dumb question is the one you were too shy to ask.
It's a shame to break something valuable on these bikes in this day and age w/ the internet a keystroke away.
I've been receiving excellent helpful advise from other riders now for over a year.
Let the experience transform you
Marshal