Rebore or rebarrel to 32-20?
This (25/20 to 32/20) is easy all ya got to do is change the barrel (or rebore it and re fit it)
Anything else (that changes rim diameter and case body diameter) gets seriously difficult
Alterations to the innards are required and some of it is tricky gunsmithing - cartridge lifter, magazine stopper, feed rails, If ya can buy Rossi parts maybe 357 mag ?
Been there done it 25/20 to 38/40