disk brake conversion question

I suspect an odd question but....I'm having to upgrade the entire front suspension. I was going to upgrade to LBP as well however, I want to wait a couple of years for that to prevent even more cost of rear axle upgrade and rims etc. That being said, I did manage to get a front LBP disk setup complete with UCA's from a junkyard donor car(73 a body), and was wondering if .....
I could find a small bolt pattern rotor to fit on the 73 spindle?
This way I can maintain sbp for a while for my existing rims, and the large ball joint on tubular UCA's will fit the spindles.