Flight 93 was a Boeing 757-222. Wiki stats that there were four different model engines used in the 757 line:
Engine|Static Thrust (lbf)|Basic Engine Weight (lb)|Length (in)|Fan Diameter (in)
RB211-22B|42000|9195|119.4|84.8
RB211-524B|50000|9814|119.4|84.8
RB211-524B4|50000|9814|122.3|85.8
RB211-524C2|51500|9859|119.4|84.8
RB211-524D4|53000|9874|122.3|85.8
RB211-524D4-B|53000|9874|122.3|85.8
RB211-524G|58000|9670|125|86.3
RB211-524H|60600|9670|125|86.3
RB211-524G-T|58000|9470|125|86.3
RB211-524H-T|60600|9470|125|86.3
RB211-535C|37400|7294|118.5|73.2
RB211-535E4|40100|7264|117.9|74.1
RB211-535E4B|43100|7264|117.9|74.1
Engine Characteristics Fan tip diameter: 78.5 inches Length, flange to flange: 141.4 inches
I don't believe we need to look at the PW engines. It appears that prior to 2002, all 757 models used the RR engines.