i only have 7mm competition and just disassembled to check clearance , and there is very tight clearance , it does not appear to have room to go up a caliber in diameter of bushing -- the guide sleeve would act as a sizer at a certain diameter , if you know what i mean -
SIZING DIE -- i think that the 300 rum guide sleeve will not have enough opening to clear a 338 neck diameter , maybe you can buy just the guide sleeve ?
you could try and send one up there and see if it touches , but i think if the guide sleeve acts as a sizer, it may get stuck
BODY DIE , a sure purchase specific for that caliber, unless you wanted to sacrifice your existing & bore it out bigger
SEATER DIE , looks like a guide sleeve and new seater plug to match your bullet type
i looked through a redding catalog & i do not see where they sell guides/parts separately
http://www.redding-reloading.com/online-catalog