Belegedhel is right. You just gotta dive in and do what it takes to make it work.
My son's 69 Globe Trotter likely had the same Bargman lock that your trailer likely had. The 69 model year has cast aluminum door frames (verify this on your trailer) which is quite thick requiring a rather long 3 1/2" set back, center of door knob to end of lockbolt.
Rebuilt Bargman locks are expensive. People buy them to keep the trailer original. I have a 75 Overlander 27'. It had a KT level style lock on it that Airstream used through the 70s. KT locks are problematic also.
So I removed the Bargman lock from the 69 and sold it for parts. Then I removed the KT lock from the 75 Overlander and installed it on the Globe Trotter. I'm hoping it will last a while, see photo.
Then I installed a new Korhee RV lever style lock ($50) on my Overlander. Changing locks is a job, but can be done by us armatures. It requires making a patch on the door skins, inside and out. It requires positioning and cutting a lockbolt hole in the door frame. And sometimes it requires three hands.
WBCCI #8607 VAC Region 11
KnowledgeBase trailer renovation threads: 69 Globetrotter, 76 Sovereign, 75 Overlander, 66 Trade Wind Such fun !