According to SAAMI specs the Swede case is larger than the Ari in all dimensions, so the chamber should clean up completely with the Swede reamer. Another option is the .260 Remington, although it may be dicey in the neck/shoulder junction. Still, that long throat may cause issues if it is oversize - shoot the rifle first to see if it is even worth the trouble of rechambering.
The Ari operates at lower pressures (40,000 cup vs 46,000 for the Swede), but the M38 is know to be plenty strong if in good condition. You could just increase your loads for the Ari until you found the typical high pressure signs then back off a couple grains, this would be a lot cheaper than a rechamber job, and you'd likely get within a few hundred fps of the Swede. Your choice.