Where to get a front pump for a 42RH (A500)

Thanks! I appreciate any help I can get. It seems like there would have to be some signal to trigger the lockup, but there's only two plugs on the trans, one for the reverse lights / neutral/park safety, and one other two pin one. I was thinking it was the speedo at first since there isn't one anywere else, but I don't know that it is since it points down into the pan. I'd heard it was maybe the overdrive control, but I was going check the manual for the truck when I get home for a wiring diagram. There are two plugs in the transfer case as well, so the speedo might be in there to account for low gear I suppose.