I'm not sure what model the JD machine is, ISMACS doesn't have a JD two letter prefix chart and Singer tells the date but no models.
I can tell you the 774 will most likely have plastic gears in it. I really wouldn't want to trust it for anything heavy like quilting. I've watched my wife blow two sets of plastic feed dog gears out of her Singer 538 and I've replaced the top vertical shaft gears on two 413s. If you can get a pic of the JD machine it would help with the ID.
I do agree with you about putting a machine in a cabinet for quilting. I'm doing two right now and using my HOTHER set on top another cabinet machine. I'm about ready to pull the cabinet machine out and put the HOTHER in.
Joe