I know this is an old thread but has anyone else here done this conversion on an Impala and used 14" stock steel rims?
There are no "stock" steel wheels that will clear a disc brake because the caliper will crash into the interior of the wheel. There are as mentioned 1969-'72 Steel wheels used on the Camaro, Nova, and the Chevelle equipped with optional disc brakes that will clear the caliper. The problem with these wheels is that they are rare making them expensive when you do find them. Additionally most people who ordered disc brakes did so on SS model cars which have rally wheels with trim rings or hub caps installed, or on the Chevelle SS five spoke steel wheels, not plane steel wheels, making a plain steel 14 inch disc brake wheel nearly impossible to find.
You could follow Jay leno's lead who had custom off sett billet aluminum 17 wheels made for his Torronado to look like the Torronado/El Dorado wheels used with big block TH400 front wheel drive. Or the 18" inch steel wheel with custom Buick full wheel covers made to up grade his aunt's Buick that he lived out of when he first came to L.A. If you want that stock look all it takes is a lot of money. just depends upon how bad you want that look.