my 64 ranchero steering wheel has 1/3 turn play. how much is normal on manual steering box? considering if i need to replace box ($700) or go with rack and pinion ($1825).

 

The manual steering on those Falcons was so easy it felt like power strg.
Did you check the entire linkage for any looseness or worn parts?
Two inches free ply was all it was supposed to have. The sector shaft and worm input have to be pretty worn to produce that much free ply. There is a sector adjustment screw and locknut on the inner side of the strg box. You might be able to loosen the jam nut ,turn the screw clockwise to move the sector teeth in and it might take up some of the ply. Please check the entire linkage before adjusting the sector adjustment. If the adjustment is turned in too far the steering will have a bind and that is no good. Make sure to have the steering wheel in the center of it's travel while adjusting.
The manual strg box required gear lube for lubrication, make sure it is full.

 

Does anyone know where to get a steering box for a 63 Mercury Comet?

 

Flaming River has new boxes but they aint cheap.

 

You might try Vintage Parts Inc.
Beaver Dam, Wisc. If they won't sell directly to you they will to a dealer.