[Aussie Mike]

You might just be better off rebuilding the old shifter Bryan or sourcing a replacement. Like any part that sees a lot of work they wear out.

I went right through and rebuilt the stock shifter in a mates XY GT. Taking all the play out of it with the correct shims etc and adjusting it correctly He couldn't believe how much better it shifted. The wear happens gradually and you don't realize how bad it's getting till it gets really bad.

Each section of the linkage where you can reduce free play will improve the shift. The rod type shifters used on your T10 and Toploaders can be improved further by using spherical rod ends where the shift rods attach to the levers on the box. These are areas that typically wear as they see little lubrication and are exposed to the elements.

Cheers