There is a console pull on an aluminum chassis that's an amp only.
Here's a link:
http://www.audiokarma.org/forums/showthread.php?t=461654
The console guys may know more.
By the time 1960/61 came around the console business wasn't the focus in the same way and there aren't a lot of 7591 based console amps built to the standard of the SA-100 (7189) or SA-300 (6CA7/EL-34) that had cages n'stuff.
There are, however, a plethora of 7591 integrateds:
X-202-B
KX-200
X-101-B, X-101-C, X-101-D
Maybe a couple of others.
Have you considered salvaging trannies from a beater 500-C and building an amp out of it? I'd like to do that some day. An alternative is to find something like a X-101-D, which is kind of fugly and build something out of that.
There's a schematic for a 500-C trash find built into an amp by Marc Stager on the Fishergroup Yahoo site marked as 500-CA.