I had mine rebuilt and still have a massive leak, can't seem to find source. I'm just checking in case I would have to replace but as of now I'm just putting out feelers.
I put fluorescent dye in mine and took a drive , it's all over my firewall but broke foot so it will be a couple weeks before I can test further.
 

Why do you want a aftermarket pump? 

http://www.borgeson.com/xcart/home.php?cat=114 they have one will need mounting bracket.

Is there an after market power steering pump for a 1955 Ford Fairlane?