Duplicating a Freightliner key, ask for this at big box stores.

All the FL’s up to 2003 used the same key as all GM’s used for ignitions from 1968-88. Pete’s up till the new key style in the mid 2000’s was the same Briggs&Stratton style ignition key Gm used in the 50’s thru ‘67.
The old GM/FL keys would unlock a lot of different locks on FL trucks after they got a little worn out they became one cut fits all. Lol!

14R1 blank is GM.

 

I keep a spare key in pocket all the time. as well for my daily as the Freightliner and Toyota both need wedges to break into without damaging anything
The Briggs and Stratton key was also used on '41 to '49 IHC trucks