I would think any heating contractor could select & install appropriate controls for your system.
Call a local.
I am looking for replacement two stage thermostats for a radiant in-ceiling electric heating system installed in 1958. Existing thermostats are Raehco, base No. TA802B1X136EL1 T802B 24V wired to replays with three wires. I have contacted Honeywell with no results.
I would think any heating contractor could select & install appropriate controls for your system.
Call a local.
RSES Certificate Member Specialist
Southwest Regional Association of RSES Secretary, 2017
If it is 24v w/relays, a good 2-stage stat, like the Honeywell VisionPro stats, could control these...BUT due to the age of your setup, call up a heating contractor and have them give everything a good lookover. Probably wouldn't be a bad idea to change out the relays with newer ones as well, but the contractor will be able to take a look at them and tell you best.