It is close, but there are differences that would have to be addressed. The steel tank has a similar exhaust layout to the later style tbird tank, but the later style tbird exhaust will barely hit it in a couple places. You could simply dimple the tank with a ball peen hammer in the couple spots, and it will work with the later style exhaust, or if you have access to the exhaust off the same MarkVIII that the tank came out of, you can run the rear section of the MarkVIII exhaust around the tank. Also, the fuel pump and sender assembly is different between the 2 tanks, so you would have to pull it out and swap your tbird fuel pump onto the MarkVIII sending unit assembly in order for it to work. None of these things make it impossible to put a 97/98 MarkVIII tank in, but it isn't simply a bolt-in swap, and if you have access to a plastic tbird tank, that would be the easier swap.