The way this thing was buggered up I never gave the most simple thing a shot 
thanks for that…any leads on whether the lock cylinder can be replaced ? 

is it possible to swap the locking latch on my 74 DT 250A with a non locking latch from another model ? If so which year tanks had the non locking latch ? Any leads on where I could find one ? 

If the website will let you, post a pic.  Those key faces "may" be mostly fixed.   You do have to disassemble the lock and pull the face off.
I use the pin in my car's roll cage to straighten out the locks.  You can make these, but ACE hardware sells the pins.
Smooth the end of the pin until it is roughly the shape of the key hole face.

Tools:  snap ring pliars that squeeze inward, roll pin, small screwdriver...lots patience.

How the key interfaces the lock or latch mechanism:


Looking from inside to outside of lock face: (you can see why a pin works to GENTLY tap it out)


After it is generally straight, then use an alum oxide wheel to smooth it, then polish it out and it will look
great again.

OR.

the easy way.  CMSNL.COM has new ones in stock.