Dave, I've been tinkering with an idea to use one of those Saginaw power boxes in a slightly different arrangement, rotated 90 degrees so the Pitman arm hangs down beside the frame similar to the OEM stovebolt box. I'm nowhere near making a prototype, but I believe it would be possible to come up with something that closely resembles the existing linkage geometry instead of what's being offered now.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!