I went the EFI route and came up frustrated with inconsistent operation. Eventually, it turned out the wire harness was causing my adventure. You can find a new harness with connectors, etc, but it will run you about $500. Also make certain you get a relatively new engine and computer.
As to 5.0 headers, maybe the shorties will work. Apparently so. I found nothing of the longer variety to fit past the steering box and eventually had the Falcon set modified into a custom set. It's great, but costly. Go shortie if you can.
http://www.hopublishing.com/0files/exhaust-2.jpg
<font size=-1>[ This Message was edited by: specnot on 5/2/06 12:32pm ]</font>