Living in the Past
SILVER Star
Here's a few pictures of the front seat. I see your problem you need to shift the seat closer to the center. Maybe the flange on the other side of the rear right leg is throwing you off. The one from the 64 would bolt in prefect. Ever bolt hole matches up and the height is right on both front legs.
Besides the two different feet on the long back seats there is a different in that the earlier used two bolts at each point and didn't attach to the top of the tub. Then they attached to the top using two bolts still at each point. Then around 70 they switch from welded legs to bent over. Also switched to single bolt at each point. So at first they had two arms using a total of eight bolts. Then switched to one arm using six bolts. Then starting using the attachment point at the top of the tub with a total of ten bolts. Finally down to one bolt at each point for a total of five.
Besides the two different feet on the long back seats there is a different in that the earlier used two bolts at each point and didn't attach to the top of the tub. Then they attached to the top using two bolts still at each point. Then around 70 they switch from welded legs to bent over. Also switched to single bolt at each point. So at first they had two arms using a total of eight bolts. Then switched to one arm using six bolts. Then starting using the attachment point at the top of the tub with a total of ten bolts. Finally down to one bolt at each point for a total of five.