It's been awhile since I had one of these apart. I'm surprised some of our other members with mid years haven't chimed in on this.
Under the shift knob is a spring that compresses when you pull up on the T handle. There is a set screw in the back of the T handle that secures the lockout to the handle. If I remember correctly you can unscrew the shift knob then simply lift the T handle, spring and lock out cable/rod out of the shifter. Now you should be able to shift all 4 gears and reverse freely. The shift lever should move all the way right and left in the neutral gate without any interference if the shifter arms are aligned correctly.
Since your T handle stays in the up position I'm wondering if the spring is in place or was lost during your repair work. If the lever catches when going right to left through the neutral gate then the shifter needs adjusted.
With the shifter in neutral and all 3 transmission levers in neutral remove them one at a time from the shifter levers. Turn each shift rod in or out to lengthen or shorten it until it fits freely back in it's shift lever hole and replace the clip. Once all 3 levers are done your neutral gate should be aligned.
I don't have a shop manual for these so I'm not sure how far the reverse lockout cable sticks up through the T handle before you tighten the set screw. It would have to be far enough to allow the T handle to rest down on the lip on the shift handle when in the forward gears or neutral. Maybe a close inspection of the cable will reveal where the screw was tightened originally. With this adjustment made, the spring re-inserted in the top of the lever and the knob screwed back on you should be good to go.
All of this is based on the assumption that all shifted well before they took it apart.
Tom