Carter rotary vane Vs formula ford mechanical

I've been researching fuel pumps for the kent 1600, and looks like the carter rotary vane electronic is the go, that was until I spotted these mechanical ones for the formula fords.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=220628369385&ssPageName=ADME:X:RTQ:MOTORS:1123

Any tips? Thanks