No way it will rattle though
Listen...we do really big inch mean drag stuff with 3.8 or a tad more --They twist the crud out of the crank and you need it! Again--.003 is not like worn out--
I help my Dad with old farm tractors and we pull some down with .008 under the spec that were still plowing! Yep OP may have been a little low but .003 on a 440 crank journal is everyday good to go. Don't be scared and blow $$ for crazy hard to find bearings--OP may drop back at idle but I promise it will jump right up and honest that is the sign of a great build to me--on one you want to Haul!