Beware!! Sears sometimes re-used model numbers. My 1950 Sams "red book" cross reference shows that the Silvertone 4586 has the 100.156 chassis, which was made by Stewart-Warner. Their listing for that chassis matches your set, Kam, but also includes a 6G5 tube. This chassis isn't listed in my 1947 Rider's index.

You might try looking at some Stewart-Warner schematics to see if anything matches up. Nostalgia Air has scans of the Rider manuals free for the downloading - check their website.