I also purchased tires from Sam's for my 84 300DT-Michelin X Metric, T-Rated. They ride really well and seem to handle relatively well. However, they did vibrate and pull to the left. I took the car back, and the balancing wasn't anywhere near close. They rebalanced the tires as well as switched sides, and not a vibration or pull to speak of now. This is the 2nd time I have this problem with tires purchased from Sam's, and they were different stores. Don't know whether the tech didn't get enough sleep or what, but I'd try rebalancing and switching sides before the expense of alignment.
Good luck...that 280C is such an elegant design.