The waste pipe (sorry if not proper name) was at one time a 4" pipe set into the concrete foundation. I need to replace the flange and it is about 3 1/2" wide one way and a little over 4" the other. What is best type of floor flange to use so I can mount the new toilet? Is it an issue to just use a 3" and use concrete screws to mount to floor (above the current tile) or does the gap in the waste pipe and flange create an issue?