Try using some PB Blaster or other penetrating oil, if the clutch is original, the bolts are probably seized in there with all the heat cycles...

Cost about $4 for a can, I personally use a Liquid Wrench product with good results... spray, let it soak for 20 minutes, then give it a go...

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2006 BMW M5 "Heidi" @ 109,000 miles
2005 MBZ C55 AMG "Lorelai" @ 165,000 miles
1991 MBZ 300E "Benzachino II" @ 165,000 miles
1990 MBZ 500SL "Shoshanna" @ 118,000 miles

(On the hunt for a good used M103 engine as of 6/10/23, PM me if you have one to sell!)