I have done this pump on the exact same van. The bolts in question are M6 high strength and are threaded into an aluminum pump housing. I used a significant amount of heat to heat the area around the bolts to break them free. I was able to get all but one out. The one that snapped was at the bottom of the pump housing, so it was easier to get at. I was able to drill out the bolt with a right-angle drill adapter. I then drilled the hole out for an M6 Hela-coill. All the other threads had to be chased with a tap to clean them up. I replaced all the bolts with studs because I knew I would be changing this pump again in another 100k miles. Sure enough, at 200k it needed another pump. It was a breeze with the studs in place because I just had to remove the nuts from the studs.