I put a 60/40 power lumbar split bench with fold down console from a 98' Silverado extended cab in my 94' Silverado regular cab. I know the floor layout between the regular and extended cab is a little different. I had to take about 1'' off of the 60 part of the bench near the hump in order to make the seat level.
All the outer most holes will line up IIRC, but i had to drill a few new holes for the inner side of the passenger 40, and the inner side of the drivers 60.
I am not sure if this is true with the crew cabs though.