It appears that you have a 55-56 column in your 57. Stuff like this happens over the years to keep vehicles on the road. The 57-59 column is exactly 4" shorter than the 55-56. If you change to the correct column you will also have to change the upper shift rod as it is shorter as well. The problem with the CPP PS unit you cited is that it supplements your original steering gear. I had one and did not like the performance. There are a number of aftermarket power steering conversion kits offered by numerous suppliers. In some cases you will have to modify or replace the column.
Fred

Last edited by rfs56trk; 06/03/2009 4:03 PM.

1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine