yes mate, mine had that surface rust too when I bought it. That's why I decided to strip it down and restore from the ground up.
I see you still have the original 4 in 4's exhaust. That's good. On mine, they were changed to the 4 in 2's from the cbx model.
The carbies are aftermarket, correct?
And you put a seat in place of the brief box carrier. I bought a cb750 kz seat (2 seater) and it uses the same hinge and lock as the single seater.
I have managed to find a CB750P brochure from the 80's (a guy in Mansfield on gumtree, used to run the Honda dealership) and the specs page says that sprockets should be 17 front 43 back. Even the cmsnl web site says the same. However, when looking at aftermarket options I didn't find these. 18 and 45 are more common. I just got a set from rpm moto in queensland.
I've tried to get Honda original parts as much as possible. It's been difficult for some parts (as it will be on any 40 year old bike) but I got most of my parts from CMS in the Netherlands
✓ CB750P 1979 (Z) GENERAL EXPORT parts lists and schematics ✓ Easy repairs with Honda diagrams ✓ Free access!
Their web site is really user friendly. Some parts I've had to look for second hand on ebay. The part numbers from the CMS website were very handy.
You have StGeorge as your location. Is that in NSW? If you are in Oz, can I suggest that if you have a lot of parts to order from abroad, don't let one order amount to more than $800 as you'll have to pay import tax on your parts too. Ask me how I know
One thing I can't find anywhere is the black rubber spacers under the front indicators on the front shield. Reason being, apparently these were not Honda items. I was told that these bikes came here without those fairings but were then installed here by an Australian supplier. Mine are all cracked and need to be replaced. Do you have any leads please?