i personally believe SPEC clutches are over rated for a 4.0.....from what i have read in my research on the manual transmission swap, the 4.0's stock clutch is a pretty strong/good clutch; thus why I went with the stock clutch for my swap. There are other "upgrade" clutches that are better than the SPEC clutch that are cheaper.
i do have to say..the spec is overpriced. I went from a Luk w/ 15k on it to a new Spec2... ilove the spec....but at double the price of a luk, eh. Although my luk was purchased from the ford dealership.....that was about $400.