Not to distract from the original conversation, I thought I'd wade in with what I found during my disc brake kit searches. Like you, Bigblock, I too didn't want to get stuck with oddball, weird pieces, so I did some asking. I hope some of you find this information useful when it comes to the kits that are out there. This obviously doesn't cover all of the kits for I didn't even talk to the Pirate Jack folks.
I talked to James (a member here at FBBO) who works for P-S-T about their disc conversion kit. The kit seems to be pretty complete with everything needed and it is base on 73 to 76 A Body dart brakes, so parts are readily accessible. And with PST you get free shipping and as B Body members you also get a 10% discount if you mention you are a member when ordering.
I also talked to Wayne at The Ramman. He too offers a kit that is based on the A Body setup. Once again, all parts are available off the shelf. Oh and you can either go with the Dart 11" rotors OR you can go with the Cordoba 11.75" rotors. Cost vary depending on which way you go but according to him, he ships everything except the rotors with his kits.
I also talked to Summit Racing about their kit. They wouldn't confirm that the kit was supplied by SSBC but other members on this forum have order this kit and said it was a repackaged SSBC kit. When asked, they said the pads were readily available at any automotive store. Just ask for pads for a "1969 Plymouth Barracuda". This doesn't surprise me since I've read about this kit is based off of the older A Body/Mustang Kelsey-Hayes 4 piston disc brake setup. Obviously the rotors for this are a bit of an oddball since you'd need the larger wheel bolt pattern but info I got from SSBC said the rotors are available for about $65 from them or Summit if replacements are needed. I also cannot help but wonder if these rotors are actually Ford Mustang rotors since they have a 4.5" WB pattern. Hmmm..perhaps some measurements are in order if someone gets a kit.
Then you have the Scarebird setup. From the members I talked to who run it, it sounds like a good setup and that it works really good. Then again by running big old Ford Galaxie rotors up front, I'm not surprised and I will probably end up going this route when I go to put disc on my '68 Fury.
Lastly there is the SSBC setup which I've heard good things about but which is VERY expensive, IMO.
Price wise the cheapest is an 73 and later A Body disc swap if you can find one. Next would be the scarebird setup which runs about $450 (est). The next 3- PST, Ramman and Summit are within about $50 to $100 of each other with Summit being the most 'spensive at $600. Then the SSBC kit is the most expensive at about a grand when ordered from Summit.
There are variables within the kits. For example the PST kit seems to come with everything from the m/c to the prop valve where as the summit kit does not come with either of those items. The estimated price for the scarebird kit includes everything EXCEPT the prop valve but you have to order the parts (they provide a list of what is needed). So there you have it! I hope I at least helped some of you with your decisions about some of the kits and what they may or may not have to offer. But other than the Summit and SSBC kits, the other kits seem to use off the shelf parts.
Hope that helps.