[Marshall V. Daut]

The trick is to get the backing plates turned as far as you can to either extreme so that you have more room to install the end plug and then tighten it with a large flat blade screwdriver. Towards that end, it helps if you take off both king pin lock pin nuts, which double as "stops" against the backing plates (ever notice the indent in the spindle where the end of the nut touches?) By temporarily removing these long nuts, you will gain a little extra distance at each extreme, just enough to make installing the end plug a little easier. Don't forget to put the nuts and lock washers back on after the tie rod has been tightened and the toe-in re-set (if necessary).
Yup - it helps to take off the front wheels and tires!
Marshall