I work at a steel structure shop, so I guess welding might not be an issue, I can always beat the crap and fire the welder if it is not properly done

That's why I was more concerned about the idea of the rivets. Where do you find rivets these days? Should they be installed hot and used a riveter like old fashioned steel building erection? Now on the welding topic, any idea of the type of material the frame should be in order to use the proper filler metal. If the repair is fully penetrated (I can check with an X-ray), did I need the reinforcement anyway? Thanks for the insight.