I'd go with a 358 RUM, ADG makes 375 RUM & 338 Edge brass that would be a simple, one pass neck down/up & go, they also make 300 RUM & so do the Peterson crew along with others, simple neck ups aren't difficult and can be done with regular dies and expander balls in several sizes/steps
This way you have all of the 358's on the power scale, max load and none of the others can catch up, then you can download to match the lesser 358's with ease, which also opens up a big doorway for multiple burning rate powders you can use
for loading ammo, just use Redding 375 RUM fl sizer & bushing dies with the correct bushings
