I had this problem many years ago with a mini marcos with SU carbs and no room for the air intake heater from the exhaust.
Hot water pipes will not totally cure the problem because these do not get hot enough until the car has been run a few miles by which time it will have frozen up and stopped.
Electrical heaters are possible, I suppose, but over complicated, in my opinion.
The best cure is to duct warm air from around the exhaust. I think that this will work even with exhaust bandage around it. You only need to get a few degrees warmer to stop this from happening.