Levi's 501's seemed to be the choice - Sometimes dyed black, but often the dye would wash out after only a few insertions, so most just left them blue or dark blue.
Update on the MSSC - From Darryl Young's book (found it)
Length 36 feet
width 12 feet
height 9 feet from top to bottom (including radom) - Photos will help detemining the actual height of the crew compartment.