You need to focus on one issue at a time.
You have one of the most powerful tools in the world at your disposal-the internet.
Just type into a search engine like Google what it is that you want, and look through the results.
Do not make the mistake of only looking at the WEB results.
Look up in the upper left corner of your computer screen and you will see that you can also
CLICK on IMAGE results. This is important because often there will be a photo of what you want and that will lead you to a website.
Buying Parts.... Do not buy from a website that has no phone number and will not let you email.
Bike Bandit .com may have some higher prices on things, BUT they have the parts for older models and they ship fast and are reliable. It just depends what part you are looking for.
Take one issue at a time.
Read that again.
Check Ebay,Check all the CB750 parts web sites each time you need a part. And of course this Web forum and its members have a wealth of information.
If you are restoring the 72 CB750 by the time you are finished you should know almost every supplier on the internet.
On a Roadstar Adventure.