Hi Gardener,
Yep, You've got a 1936Hart-Parr 70 with a 5 gear engine.
For a water pump, try contacting John Holcomb in Mi. I haven't contacted him inb about 4 years but the info I've got is;
Phone (231) 843-2663
<!-- e --><a href="mailto:Holcomb@t-one.net">Holcomb@t-one.net</a><!-- e -->
John used to specialize in 70 water pumps.
I used a later muffeler on mine and made it work, I don't know if anyone is selling new ones for the H.P. 70's
Just go to your local NAPA store for the belts.
Your carb should have a small metal tag with the numbers on it.

Good luck, Larry Coltrin