Be aware also that there's a to 04.02.79 and from 04.02.79 tanks. Difference is the the latter has the rollover vent valve in the top of the tank, and needs a hump in the center of the floor to clear. Before 04.02.79 has a vent tube in the front of the tank with the vent valve under the right front floor, near the cowl.
Minor diff in the trunk floor is after April 77, the spare mounts on the rear axle kick up under the rear deck, instead of in a spare tire well.