The PEP-66 is originally designed to hang on a Slocket. The HSF can be used on S370 and Socket A mainboards. There's a catch. If the PEP-66 is left in its original configuration, it lays flat on a mainboard. Not too many mobo's have the real estate required to accommodate the PEP-66 with a 25mm tall(YSTech 27 cfm, or Delta 30 or 38 cfm) fan. I believe that the Abit KT7 can(barely) accomodate the PEP-66T. This kind of PEP-66 comes with a little ~20 cfm, 15? mm thick 60mm CPU fan.
To use all of the cooling capability of a PEP-66, with a 25mm tall CPU fan, it must be hacked for use on a mainboard. It's not difficult, as tin snips are the only tool needed. Then the PEP-66 will stand vertically on the Socket 370 or SA mobo.
I don't remember the exact difference in performance between the PAL-6035 and the PEP-66. I think it's safe to posit that a PEP-66T(with the wussy little ~20 cfm fan) works no better than a PAL-6035 with a real fan on it. If that indeed is the case, and you don't wish to modify a PEP-66 so that it stands vertically on your mainboard, the PAL-6035 is the better choice.