GM has had this problem from year to year and engine to frame problems. It's no "biggie". You didn't sate whether this was a vertical clearance prob or what so I will just state that the 3 bolt motor mount is the same between big and samll blocks. Try the spacer that GM provided on so many cars to give yourself clearance upwards (away from the mount) Dealers and salvage yards have them cheaply and "by the dozen". Hope this helps.