The angles used for a Monarch Superspeed and a modern day Superspeed are absolutely NOT the same.
To maintain a 50x100" playing surface, there are some who use K66 cushions, mounted directly to the unmodified sub-rail. However, If you mount it at the top of the sub-rail, the nose height will be 1 1/2" high. That said, the folks who do it, drop the cushion 1/16" lower, when they mount it. This leaves an unsightly ridge along the top of the rail. Some of these same folks will belt sand that ridge away (not advised.. Any of this...)
You can mount modern day K55 cushions to an unmodified sub-rail, in the standard mounting location, and the nose height will be about 1 13/32".
The basic nose height dimension that is commonly referenced is 1 7/16". However, the common height that is used by most of those of us who actually modify the rails is 1 29/64".
If you use a standard K55 cushion, the table will bank a bit fast, and slightly short.
See attached photos, for reference.
This information is completely factual, and based on MY OWN FIRSTHAND knowledge, from trial and error. This information has also been cross-referenced with some of the few other folks who also perform this service.