i hear the bottom ends on a 3.0 will handle over 6k but the valve train wont thats what i always wanted to do to mine was upgrade the valve train and make it a screamer but i put 302 in it
you just have to take your time it will pull it gain speed before the hills and let it slow you down i used to haull full size mud trucks on trailer behind mine when i had the 3.0 auto with 3.73s and 35s