Yes they should all work fine, the plastics for sure, the flares from an 88 will but you may need to drill out the holes for the push pins as the 88's would have had screws. The floorboards from what I've been told will work assuming you mean aftermarket, if they are the stock half floorboards then they will work for sure.
Does anyone know what other fender flares will work on a 96 300 . I just can't see spending 300 to 400 bucks on some for a 300. Think about it is you can get a kit for a 400 for 90 bucks . Was just wondering if they would work