Yesterday we were adjusting the valves on my son's 280SL and found the exhaust cam on the # 3 cylinder is starting to wipe. Can the cam be replaced without removing head? My son has limited funds(in high school). Where to find camshaft?

TIA

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1989 Arctic White 190D 2.5l auto w/400E Brakes and a 5spd waiting for me to install

1977 280SL Euro M110/w 4spd

2001 Dodge Ram 2500 Quad cab 4x4
dyno 383hp / 916ft#'s