No quick recommendations but some words of caution. Steel strings will exert more downward pressure on the cone than nylon strings if tuned the same. I don't think the cone will fail but the additional downward pressure could be enough to screw up the action, buzzing being the probable result. If that occurs, you will have to have the action reset on your instrument which is not an easy task with resonators. Another thing to consider is the neck. If the neck is not reinforced, it may not be able to stand up to the additional tension of the steel strings.
Also, when you change out the strings, change them out one at a time and bring the new string up to pitch before you change out the next string. This procedure will keep downward pressure on the cone at all times. Resonator cones don't like to be completely relaxed and then tightened back up repeatedly. It's not good for them so to speak.
Good luck...!!!