Disk brake help

Thanks for all the advise. OK seems I really need to determine if I indeed have a 73 set up, that's how its looking.
The only reason I thought this was a small bolt pattern is because I was tire shopping and the guy mentioned if I wanted bigger tires for rear I'd need to go to a 15" rim and I had a small bolt pattern. Apparently Goodrich doesn't make the 255/r14/50's that I had on my Duster anymore. What are the measurements between bolts on LBP and SBP?
I didn't know I could move the calipers to rear of wheel. Is it a simple swap of Left to right or is more involved and is there any advantage other than I can add a sway bar?