Model Year Differences

91-93 did not have dual exhausts. Compared to the later years, the transmission cross member on the 91-93 does not have clearance for the dual exhaust on the driver's side. The exhaust combined by the flywheel and went to the passenger side. The other difference is the driver's side floor pan. Is was never intended to provide clearance for suals there either.You can try the 94-96 cross member but expect to make floor pan mods as a result.
Clear image makes a tubular cross member specific for the 91-93's. It will keep the pipes pretty much next to the drive shaft. The other issue in the rear is clearance around the fuel tank fill pipe.

Dave

The Clear image cross members for the 91-93s keep the driver's side pipe in the same place as the LT1 cars. You do not have to modify the floor pan for them. If you want to run symmetrical duals (make the left look like the right) you do have to clearance the floor for anything over 2.5 inches. You can squeeze the 2.5 inch one under the car without hitting anything, but it is close. You may have to cut the second bolt hole off of the end of the drive shaft loop to allow the pipe to pass it. If you go any further toward the side of the car, you have to clearance the floor pan. If you choose to clearance the floor pan on the driver's side, most of the change will occur under the driver's seat. If you feel like spending some money, you can get preshaped oval exhaust elbows and you can run them without worrying about clearancing the floor pan. If you want to put duals on a 91-93, you can get a second muffler hanger from the right side of another 91-93...the bolt holes are already there to mount it. It uses the same bolt hole as the CV/GM sway bar mod. Some of the early front markers had yellow and clear lenses as opposed to orange and clear. The headlight harness for the LT1 cars is different from the TBI cars. Only the RMS has 4 horns (and FW).

If you want to disable the push pedal to shift, just disconnect the solenoid on the steering column.

Added oddities: heater fan and controller screws are 7mm heads on 91-93, and 5.5 on 94-96. The gate glass seal is different from 91-93 an 94-96. Gate hinges are different from 91-93 and 94-96. The hood liner/insulator for the 91-93 is shaped differently for clearance than the 94-96 (91-93s do not like the newer insulators). Some early 91s have different wheelhouse extensions, and the hole pattern for the side airdams are different. The driver's side wheelhouse extension is different after 93, and the bolt holes are located differently. There are two sizes of drip pans for the AC box (I am not sure which car has which one (I know a 93 RMS did not fit my 92 OCC, it was about an inch longer front to back). T/he passenger's side cowl has the wiper stop closer to the center on the 94-96 cars.

Of all these 1991-1996 cars only the Roadmaster Sedans allows for the rear door windows to go all the way down.

The sedans were only made from 92-96. The rear door windows have a stationary glass at the rear of window opening. The Fleetwood has a similar stationary panel, and the glass goes all the way down as well. The rear regulators for the RM sedans do not fit the wagons.

A member of ISSF has successfully mated the sedan regulator and glass to a wagon rear door. It took some modifying and to me the end result was ugly.

I don't ride back there and my A/C works so I couldn't care less if they go down all the way or not.

It is also a safety factor that keeps kids from hanging out of the open windows.