I can help on some of the questions.
Look for headers designed to fit C-6 equipped cars. Generally, if they fit around a C-6 they will fit around the somewhat smaller FMX. I haven't looked up the part numbers but Hooker still offers 351C-2V headers for the 72-76 Torino Chassis.
I can't really advise you on the tranny upgrades but I suggest you post or do some searches on the Ford Tranny Forum:
Ford Tranny Forum
Also my 73 Gran Torino Wagon has an AOD. It was already installed when I bought it last April on Ebay.
Radchero / Kev
<font size=-1>[ This Message was edited by: Radchero on 8/16/06 1:45am ]</font>
<font size=-1>[ This Message was edited by: Radchero on 8/16/06 1:46am ]</font>
<font size=-1>[ This Message was edited by: Radchero on 8/16/06 1:47am ]</font>
<font size=-1>[ This Message was edited by: Radchero on 8/16/06 1:47am ]</font>
<font size=-1>[ This Message was edited by: Radchero on 8/16/06 1:49am ]</font>
<font size=-1>[ This Message was edited by: Radchero on 8/16/06 1:50am ]</font>