HH
Did some looking at the 300 , none of the factory 308 bore barrels will work for a re-chamber so your looking at a total re-work , bore and chamber , thats going to run around $300 or up + Donor barrel .
As for the 35 Rem , you can get that done for around $100 to $150 plus the cost of the barrel , depending on who does the work .
stimpy