Looking at buying these wheels but am unsure how to read the date. Any help would be appreciated!

The wheels are straight and true, and look great. I looked them over
carefully yesterday. On the high spots around the lug holes, GM 68 is
stamped on one raise and NT is on another. FC is stamped to the left of
the valve stem, and if you hold the valve stem at 6 o'clock, 3028 is
stamped at 11 o'clock. On the inside of the rim, on the bottom well, is
stamped: made in USA 14>6 JK NT B8 C.

Those are 1968 steel wheels for cars with drum brakes. Looks like they were made February of 68 judging by the date code of B8 inside the rim.

Will they work on a disc brake car or are they different? Mine is actually a July built car but any FC's will work I guess.

To my knowledge FC coded are for drum brake cars and XF are the steel wheels (14x6) for disc brake cars. I think FC was used for a few years. I dont think they will work if you have disc brakes, I dont think they will clear the calipers.