Borgeson Steering Swap Question About The Pump

I'm looking to do a borgeson steering box swap on my 68 xr7. I'm trying to save a few bucks and possibly buy the pump from somewhere else for a little cheaper. Does anyone have a part number that is the correct pump for completing this swap? I've read that this is a common pump for GM vehicles; but haven't found a part number or what exactly it comes off of. One other concern is that the box I believe is suppose to have about 1000 psi; just making sure this information is correct and that this pump matches.

My pump isn't good and would need replacing anyways which is why I'm looking at getting a GM pump. The water pump on my windsor is different mounting bolt location for P/S pump bracket so I would have to modify my existing modified bracket to adapt to the GM P/S bracket. If the GM pump is a standard part on many applications then I should be able to find a GM guy or dealer who is selling one for cheaper than the $300 that Borgeson is selling at. So what I am looking for is either a GM part number or a O'Reilly's part number to cross reference so that I can try finding this pump at a different price.

Well I've continued looking at pumps on the internet and have a new question. What is the saginaw pump pressure that I should be looking for. I know I said earlier that I've read you should be looking for around 1000 psi but all the pumps say for their description is not a pressure rating but rather the application that it is for. Should I buy a pump that says it's for a mustang rack and pinion set up or stock gm set up or what? What pressure are these rack and pinion pumps rated for?