Make sure the end of your shifter is in good condition.
Check first gear the big'N at the rear of trans if its sloppy on the shaft it could also be an issue.
As far as a shift fork issue its had to tell without a good one to match it up to you would need it out to match it again a good one, if you had a experienced eye its possible to see how it matches up... you can drive the shift rail forward and remove the shift fork..
BTW the ball for the detent is 3/8" all used on those tractors are 3/8"...
A look at whats spose to look like when all's well...https://fordtractorcollectors.com/4-speed-transmission-locked-up-stuck-in-two-gears/