I can tell you why your boxes are binding . They weld a 605 box onto the cut off lower section of a 1959-1964 ford box . They are using both bearings on the sector shaft (the one from the 605 box and the one from the old ford box) when they weld the two half's together and don't get them perfectly square the sector shaft will bind . Now add heat and the sector shaft will really bind causing a lock up ,this is why a P/S cooler helps .
There is a slight float in the 605 box when driving ,this is from the gear mesh from the non P/S sector shaft gear and the 605 rack gear . There is a break in period for this of about 500 miles or so then the box needs to be re adjusted and the float goes away.
The 605 box is not a bad box in itself . I have built 605 boxes for 57-59 fords and still have one in my 58 ford (6yrs) with No cooler and using the 58 eaton P/S pump ,I have never had a problem. No I don't make 605 boxes any more. There are better boxes out in the world and thats what I am working on now.