Rechamber,open up bolt face, extractor and receiver rails, and feeding ramp. May require slight lengthening of magazine (you did not specify which action/rifle you are converting. The cost benefit of conversion are questionable. .375 is min cal for most safaris and ammo is not as readily available as 9.3x62 which is making a comeback. Loaded to equal pressures the 9.3x62 holds it's own and allows an extra cartridge in mag. If handloading is not an option the 9.3x66 (.370 Sako) would at most require a slight lengthening of mag. depending on action used. IMHO not worth it. Better to put the conversion costs towards a .375 Ruger or H&H if you need the extra power.