This was clarified for me, so I will attempt to clarify it for you. The clutch itself is not hydraulic. You can use pretty much any clutch in a hydraulic or a mechanical set up. It's the actuator that makes it hydraulic. You will want to get a kit like the one that Keisler has:
http://www.keislerauto.com/gm/gm-par...ypage_acc.html I got that kit and so far like it, although it has not been installed. The main reason I chose that one is there are no mods or welding to the firewall. It includes a bracket that sets the proper angle for the master without having to weld on an adapter plate. I know that Classic Motorsports Group (Classic Chevy 5 Speed) has a Hydraulic actuator kit, but could not find a link on their site to buy it separately.
As for what clutch to go with....what is your setup? What engine are you running? LS, SBC, BBC? What are your plans for the car? Alot will depend on that and what your are running for hp/tq. If you're running a LS, lots of guys on here will recommend the stock GM LS7 clutch, which from what I understand is rated to 500hp at the wheels. I'm doing a LS conversion and decided to go with a Monster clutch. It's been given very good reviews at
www.ls1tech.com For a SBC or BBC, quite a few guys are running a dual friction Centerforce clutch. I'm sure other guys will step in as my knowledge in clutches is VERY limited and I'm just passing on what I was told. Hope this helps some.