I think what they sell is a signalstat. Where its a 900 or 800 model I don't know. Doesn't make any difference, both are good and have been around since the beginning of time.
You may have to remove most of the grease from inside the unit and replace the internal bulb if you want it to be bright enough to actually see it. I think the bulb # would be 51 if my rememberer is working. Also, run a separate ground wire from the controller.
I stick the wires inside a period style loom in a feeble attempt to make it look like it was made that way.
You may also find that the flasher is junk. Most new thermal flashers are. I find that old flashers are of much better quality. I also haven't found any new electronic flashers that work.[ probably just haven't tried the right one, but, I've tried a bunch]