[Grady Clay]

Sean,
For 1971 the transmission serial number and type number are on a raised area of the casting under the differential.

First let me first address some external issues.
You will need to clean, inspect, replace the clutch cable, the plastic piece at the transmission, the pivot piece at the clutch arm and the plastic hemisphere in the clutch arm. Your car should have the up-dated pivot for the clutch arm.
Inspect the loop on the transmission differential side cover for wear. If damaged it can be repaired with an insert.
The clutch release bearing guide tube should be modified by grinding a small drain grove in the flange. The purpose of this is to provide a safe path for any transmission oil that should leak past the input-shaft seal. Additionally you should add a seal inside the guide tube to act as a “dam” for transmission oil coming past the input-shaft seal. All this helps prevent gear lube from damaging the clutch disc.
You will want to remove the axles and clean and re-lube the CV joints. You will need new CV gaskets (4). I would recommend new axle boots (4), clamps (8), and new Skorr washers (16) under the CV bolts. Carefully inspect the CVs and the bolts. When you take the axles out, put the stub-axles back in the hubs and torque them (at the wheels) if the car is going to be on the ground, otherwise the rear wheel bearings can be damaged.

Follow the workshop manual for transmission removal. I would remove the engine and transmission as a unit unless you already have the engine out.

Once the transmission is out of the car, you want to get externally perfectly clean! Red-beard is absolutely correct. The transmission was originally covered with a Valvoline product “Tectyl” that is basically cosmoline. It comes off with Stoddard solvent but after 32 years it will take some elbow grease. After reassembly, you should re-apply this coating to prevent corrosion. More about that later.

Don’t get the starter soaked in solvent, it doesn’t like dirt, oil and solvent inside. There are two starter motors available; a 0.8 HP and a 1.5 HP. It says on the side of the starter. Hopefully you have the 1.5, if not, I recommend exchanging for one.

Are the rubber boots at the shifter, clutch cable, back-up light switch, starter cable, and speedometer drive all in good condition? If not get them ordered now as some may be difficult to find.

Get the transmission warm inside and then drain the oil. Carefully inspect the magnetic drain plug for ferrous material and transmission parts. Clean the external surfaces again. Upon reassembly, one grain of sand in the gears can do a lot of damage. Now is the time to get it perfectly clean.

Follow red-beard's advice about soaking the fasteners with some penetrating fluid for several days.

Please be careful with all these solvents around. We don't want to visit you in a burn ward or worse.

More to come.

Best,
Grady