I'm into Fieros and I'm examining Isuzu gear ratio options for the Isuzu 5 speed used with the 4 cylinder Fieros.

This site: http://www.scca.com/documents/Club%2...rovedTouring.p df
Lists the '88/'89 I-Mark non-turbo SOHC as having either a 3.73 first gear or a 3.27 first gear. I'd like to find a box with the 3.27, IF it even exists.

www.car-parts.com gives the following options for '88 Isuzu Imark transmissions:
M.T., w/o turbocharged; "RBD" interior code, w/o cruise control
M.T., w/o turbocharged; "RBD" interior code, w/cruise control
M.T., w/turbocharged
M.T., w/o turbocharged; "RBB" and "RBC" interior code

and the following for '89:
M.T., 1.5L (4 cyl), w/o turbocharged; "RBD" interior code, w/o cruise control
M.T., 1.5L (4 cyl), w/o turbocharged; "RBD" interior code, w/cruise control
M.T., 1.6L (4 cyl)
M.T., 1.5L (4 cyl), w/turbocharged
M.T., 1.5L (4 cyl), w/o turbocharged; "RBB" and "RBC" interior code

Does anyone know how to tell which is which and what I want?
What do the different interior codes mean and how do they relate to engine type?
Thanks.