The strut tubes are apparently a little smaller inside on the ABS struts than on previous models. And there's some spacer at the bottom that needs to be removed for the Bilstein struts that is apparently welded in place on the ABS struts, instead of just being nestled down there between the strut and the cap that bolts over the bottom.

That being said, I have a set of Bilstein HD's in my ABS equipped 240. The strut was such a tight fit in the strut tube that I even had to scrape off the vary thin plastic labels on the strut to get it in. I think others have sometimes needed to lightly sand the inside of the strut tube and even remove the paint on the strut to get it in. As for the spacer, I couldn't see any reasonable way to remove them, so I tried the struts with them in place. The gland nut (the large nut that screws in on the top to hold the strut in the strut tube) can't seat fully with the spacer still there, but a substantial amount of threads are engaged, enough, IMSTO (in my shade tree opinion), to hold. I put thread locker on the threads to make up for the lack of the base of the gland nut torquing down onto the strut tube, tightened them snugly, and put them back in the car. So far over a year of use (with IPD sways and lwoering springs) and no problems at all. No clunking, and I've peeled the dustcovers back and looked at the gland nuts a couple of times (possible through the spring) and never seen anything that would indicate they are loosening or allowing the strut to wiggle.
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'63 PV544 rat rod, '93 Classic #1141 245 +t