f. boyle-
Read the thread in the Parts and Accessories forum about the SB clutch mistake (turned out ok in the end, though). Something about needing to match the clutch to the HP/ tq you plan to eventually reach. I have had several stock clutches (several trucks, one clutch per truck) hold up under 600+lb-ft towing GCVW of 20K+. But like most other thigns for these trucks, performance parts are only a hair more than stock replacements. I would recommend aginst a LuK Pro Gold. Not a bad clutch, but it still got just as hot as the stock clutch in my 92 W250 I had 2 years ago. Didnt engage any firmer or more positive than stock. I still have the stocker. Waiting for my clutch to go out if it does; guy in Colo Spgs will do a performance rebuild on it for about $325. Says he's had several customers with 2nd genners hold up well towing.
Daniel