The platform looks good in your picture.
Below is a page from the 1955 Cub operator's manual with some of the extra cost equipment for a 1955 Cub. It has a pic of the spring.
http://farmallcub.com/rudi_cub/www.clea ... e%2072.jpg
The Fast Hitch was available beginning in late 1954, at Cub serial number 185001.
If your Cub is a 1953, someone added it.
Just some info, maybe you knew already, the Depth Control lever on yours, to the right of the seat, looks like one for Cubs with a drawbar.
The Fast Hitch lever was different. The first Fast Hitches had the lever, IH changed the lever to a crank in about 1957.
It would be interesting to see how yours is connected to the Fast Hitch.
Below are pics from TM Tractor, showing the Fast Hitch lever.
