Those do look similar to my brackets ( except the ones I got appear to be little taller for the deeper K-30 frame rail sections - hard to tell in this pic ) but I did not know that they came on a K-20 frame ?
I was under the impression that these were a Crew Cab K-30 only frame brackets - is your K-20 frame a Crew Cab ( which uses a 1-Ton fraIta