I I did a quick search, looks like the 7.00x18 is pretty rare. Coker has a reproduction Firestone in that size, but it's a car tire. If your truck is just a cruiser and not a worker, they should hold up fine. They also have STA and Deka tires. They're both a little pricey, $200-250 for the STA and over $300 for the Deka. Not to mention rim flaps and tubes.
BTW- the STA Traxion tires are actually more of a mud tire and not the one in the Coker picture.