Jim,
Here is a example of a used one on ebay. It is the older design. Expect to see these from 500-650 as this is.
http://cgi.ebay.com/ebaymotors/HOLLEY-PR...sQ5fAccessories

One controlled with a Holley Comander 950 would be better.

You can also do as Beater is doing. Use one from a TBI Chevy truck 305 or 350 motor and control it with a Megasquirt CPU and make your harness.

A TBI will work better than Multiport, because of the siamese intake ports.

Inliner Member 1716
65 Chevelle Wagon and 41 Hudson Pickup
Information and parts www.12bolt.com