74 has the vapor recovery tank in the fuel tank thus the large hump up on top. 73 has a small external vapor tank up on the shock cross member.
You can use the 73 tank and get the small external vapor tank or do away with all together.

72 Satellite Sebring Plus 440, 72 Dart 5.9 4-spd, 68 Valiant, 73 W200, 78 D100 sb, 78 D200, 98 DAKOTA, .
Moparmarks Parts & Restorations
Desert Mopar Metal
Grand Jct. CO
970-261-7039
http://moparmark.com/
motormangj@gmail.com