Yes, they are the same! There were actually 3 different tanks used back then.
The early CSi tank utilized bayonet mounts for both the fuel sender and fuel suction device. Around 1973, the fuel suction device was changed to a bolt on design, while the sender unit still retained the bayonet mount. These 2 tanks were both mounted from above (dropped in trough trunk).
74 and after CSi tanks were mounted from underneath car. Fuel suction and sender units were the same as the 2nd generation tanks. The fuel filler neck is now integrated (welded) into the tank whereas the earlier tanks use a rubber filler piece between tank and filler neck. Don't know whether this style tank can be mounted to earlier cars though.