When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
53-56 is a direct replacement, note that the steering column shaft is part of the gear box. Finding a usable stock box is the problem, there were of a pretty basic (i.e. crude) design that required regular but seldom done maintainance to not destroy itself.
You may want to PM or email Ferguson with your email addy (note: you must encript your email addy by substituting the word "at" for @ or "dot" for . or something similar or it will be automatically stripped from the message by this forum's software) to get a preview copy of the new tech article on steering choices he and I just did to read all the pros and cons of what is available to you.
The 53-56 will work but the 53-55 are exactly the same. The 56's steering coulmn is 1" shoeter due to the usage of the "life guard" steering wheel. The only internal difference is the worm gear and shaft is 1" shorter. If you intend to use a 53-55 steering wheel with a 56 box and column you may end up with not enough room between you and the steering wheel.