I need help to overhaul 7-tooth steering

[Rich in Tucson]

The new worm should be a press fit. I use a 20 ton press that is barely adequate to remove old gears but has no problem installing new ones. The gear is pressed on beyond the groove in the splines which is for a circular keeper which is covered by the recess in the gear. Your lower bearing surface looks better than that on a NOS shaft I have!