front end swapped to disks, what axles do i need to swap in so my lug patterns match?

The PO on my scamp was ambitious enough to swap out the front drums to discs and rebuild the front suspension, but now i'm left with two different wheel sizes which makes carrying a spare sort of a gamble. Is the simplest solution to just swap out the axles? If so what am I looking for and what else will need to be changed (obv, drums and hardware but anything else?) Or should I take this opportunity to go disk in the back as well? I'm looking for the cheapest way to do it right and am perfectly happy with the braking performance now.

Thanks for your input.