You do need front and rear plates in Iowa and they need to be mounted on the exterior of the vehicle. I've gotten by for about a year with no front plate but was eventially given a warning and had to then prove I had a front plate properly installed. I also had to pull my tint off the front door windows.
My feeling is: why give law enforcement a reason to stop you? If they do and you have illegal tint, clear corners, loud exhaust, tinted taillights, (all of which is illegal), your problems might be compounded.