I stuck with the 11" clutch. I'm using a Ram diaghram pressure plate and a Ram disc. The pressure plate is gold in color (indicating one of the certain type models I assume) and was in the car when I got it. I had gone with a Hays unit when I rebuilt the car in '03 but when I broke the car at the strip (long story - not pretty) I replaced the flywheel with a Centerforce sfi rated forged steel model. The instructions said there was no need to have it surfaced so I didn't - and shortly thereafter it started slipping. So I had the Ram pressure plate rebuilt here locally, bought a new disc and had the flywheel surfaced. It works so much better than the Hays Long style pressure plate (3 finger) I was using before this one and the Ram pp is thinner than the Hays unit making clutch adjustments on the clutch rod a whole lot easier. I'm making some good power out of my setup and it hasn't failed to hold yet.
The 383 was the only big block using the 11" clutch in '69 if I remember correctly. Not exactly sure why, unless it had to do with getting the car moving with the smaller inch big block engine. In 1970 they went with the 10.5" unit which, if I remember correctly, was actually a 10.95" scalloped unit. I'm not quite sure about that, though. At any rate, I'd stay with the stock size clutch just to make sure everything else fits up. And as for what manufacturer, well, there are a lot of good ones out there but the Ram products have been good to me so far.