So because I have bags of money lying around (yeah, right) I'm planning to buy three lowers to ultimately build three rifles as collector items/huntingrifles/range rifles.  The end products I'm shooting for would be:
6.8 SPC
.458 SOCOM
.308
Do I understand correctly that I would need to purchase two .223/5.56 lowers and one .308 lower like AR-10 from Armalite?  And then the proper uppers?  
Thanks (and sorry if this is the 2000th time this has been asked this month)