303-25 what?
Elaborate on the cartridge. Do you want a 25 caliber on a .303 case? Or a .303 caliber on some .25 case?
"The .303/25, sometimes known as the .25/303 is a wildcat centrefire rifle cartridge, based on the .303 British, necked down to fire a .257 projectile, originating in Australia in the 1940s as a cartridge for sporterised rifles, particularly on the Lee–Enfield action; similar versions also appeared in Canada around the same time"
https://en.wikipedia.org/wiki/.303/25
Any gunsmith experienced in rebarreling could do the job.
Finding a 'smith with the reamer might be the challenge. Don't know if Epps still has Elwood's old tooling.
This would not be an inexpensive project.
Cost of barrel; cost of reamer, if one has to be custom ground; cost of gunsmithing; cost of dies.
If one of the higher grade Parker Hale conversions was the starting point, an attractive, good shooting rifle could result.