I believe that's the same chassis used in my barberpole.
http://antiqueradio.org/philc12.htm
Predictas are like the girl in the nursery rhyme, the one with a curl on her forehead. When she was good, she was very, very good, and when she was bad, she was horrid.
$50 is a good price and Predictas are well known. There will probably be some cussing before you finish the project, but you'll have no shortage of armchair quarterbacks.
Phil Nelson