I knew That was going to be mentioned, I don't now about that.
98's bumper stickes out more. The engine sits a bit highier in the 98 because of that engine support that they added in the front on the 98.
( The Front end is higher) The Hood , the windshield seems a bit longer in the 98 , inside of a 98 the glass's bottom is farther away from the passenger than a 97 which is closer inside.
Then if you do change to the 98's bumper with that different shape and that big chrome molding, then what about the rear bumper which is very different. You can't interchange the back also.
Why go with all that trouble. Might as well just get a 98 if you like the looks better of that year. 97's and 98 are in the same price range. If any difference maybe $200 to $750.
Even if the conversion is possble. It will cost over a $1250 to do it. That plus another $1500, you can get yourself a good running 98.
I don't know about you but it's all hopeless.