Altho it seems like fuel pressure probs I'm still thinkin there's some fruitful research at the below reference (the "Handbook" as well):
Keep talkin ~
Still, a pic would help ID ur system.bubba22349":3tt2plue said:There isn't much if any vacuum advance at idle and Yes yours is a very common problem. Most newcomers to these early Ford six'es just don't understand how the distributor (LOD) and carb's (SCV) work together, it's not the same as the typical vacuum advance systems and requires some different testing. There is an excellent article that will help you in getting to know how they should work ( see below link) and then you will be able to figure out what's causing the problem. When everthing is right and in good condistion a 200 will idle smooth down to 525 - 575 RPM in drive many even lower. Have you done a compression test yet or tested the plug wire resistance? Good luck
http://www.classicinlines.com/Loadomatic.asp
Stock 1966 Ford Mustang tune up specs
Plugs are gaped to .034, Points are set to 39 degrees Dwell or gaped them to .025,
Base timing is 6 degrees BTDC with a Manual trans or 12 degrees BTDC with a Auto trans, Idle RPM in drive (AC off) 600 RPM (650) with Manual trans 525 RPM (575) with an Auto trans. Numbers in (575) are for engines with California Emissions.
Keep talkin ~