323 355 or 373 gears??

IMHO before you start spending, I'd make a list of all the problem areas you will be creating with all these changes and the parts you will need.
Sometimes making a change, requires making two more to keep it right. It's definitely going to cost. Seems like U R over doing it a little but it's good to dream.
I think the guys on this site will help you with your list. But they will need more info..