changing bolt pattern

IMO, Kind of depends on what you will want to put yourself through.

1) donor as mentioned by red cuda would be best option especially for the front

For other rear options you...........
2) could buy new custom axles with the larger pattern and drill current drums to fit
3) could rework current axles and drums (weld up small pattern and re-drill for large, see pics)

4) last resort would be wheel adapters