I don't think any of the three are an optimum choice. Where did you get your TKO, and was there a reason you chose not to get a complete kit? What are you doing for a crossmember?
Looking at the choices above in order, I saw:
Ram info HDX Performance Clutch sets
GREAT DRIVEABILITY AND PERFORMANCE TO 450 HORSEPOWER
Might be okay. Lots of feedback online by googling, like this http://www.stangnet.com/mustang-foru...clutch.781293/
I think if you go Ram, IMO the Powergrip may be a better choice
Powergrip Performance Clutch sets
MUSCLE CAR PERFORMANCE TO 550 HORSEPOWER
As power levels move up to and beyond 500 horsepower. RAM POWERGRIP meets the challenge with a combination of organic and metallic disc friction surfaces that effectively increase the clutch capacity to the 550 horsepower level. The 8-spring hub is equipped with RAM POLYCOIL damper springs encapsulated in polyurethane. This spring can handle three times the shock load of just the coil spring, and is standard in all RAM competition discs. The RAM Competition pressure plate in this kit provides 30% more clamp pressure than stock, and meets SFI specifications. At this high level of performance RAM POWERGRIP provides surprisingly good driving characteristics with smooth, comfortable driver control. Sets include pressure plate, disc, release bearing, and alignment tool unless otherwise noted.
The McLeod part number (note 350 HP) http://www.summitracing.com/parts/mcl-75125
I think if you went McLeod, you'd want a Super Street Pro ( http://www.mcleodracing.com/products...Street+Pro.mcl
When I installed my TKO, CC5S (now Hurst Driveline Conversions, HDC) recommended a McLeod Dual Performance diaphragm style clutch kit, and it has been the best clutch in any vehicle I have ever driven. No more pedal effort than the hydraulic unit in an 85 S-10 I used to have, and with street tires and a mild BBC (right around the same ft-lb as your SBC) it clamps plenty hard, no chatter or slip (was broken in correctly). I cannot find anything in the McLeod catalog now that looks anything like my clutch. HDC now includes Luk clutches in their TKO kits, but I don't know which model/style. Likewise, Keisler does not list the manufacturer of the clutches in their kits.
When I googled the Hays part number, I could not find any info on HP/torque capacity, but I see that it is sold at Advance and/or Autozone, Sears, etc. Not sure what that says about the performance level of that product...
You say you spoke to each company; did each tell you these particular parts numbers are up to the levels you need? I mean, when I see the description for the Street Pro with 350 HP, that would make me a little concerned. Some subscribe to the theory that it is better to go with a less strong clutch in order to have it fail before other driveline components like R&P, diff, axles, trans, etc. With street tread radials (no drag style radials), I personally want a nice strong clutch; my tires will break traction long before anything else breaks (knocking wood right now), because with all that torque on tap I don't need to do 4000 + RPM clutch dumps.
So again, either some of the published info is wrong, you talked to a sales or tech guy that doesn't know their products at some of the companies, or you do want the clutch to be the weakest link by far.