If there are half a dozen threads or so at the further depth, I would still use a longer bolt, and frankly antiseize (on all the bolts!), or you are just creating problems if you ever need to do this again. Dealing with a stud turning and such is just not worth it. And unless you pull the stud out of the block, you probably can not install or remove the pump with it in place. Stick the stud, and double nut city, if you have enough thread external to the pump flange. If not, you are back having a problem. Another wise move is to change the bolt that is interfered with by the aux pulley (which is probably the bolt in question) to a socket head cap screw (allen), you can generally wish that past the aux pulley without having to remove it. I am doing that on my S4 that I am also changing the pump on. I got a rebuild kit for mine for $30, and the tool to insert the seal with for $25, and rebuilt it myself (see hussie the S4 on the lotustalk.com esprit forum). Good luck Neil, Brian