I have the 190 in mine and even towing 24,500 pounds there the mountains ive never seen over about 205 to 210

 

190!!!

 

I have a 53 block also and im going to get a 190*. Regardless of WHAT temp the stat is its the PRESSURE that stresses the block. SO with that in mind the blow off pressure of the radiator cap would be the killer i would assume.
My radiator was PLUGGED with mud from a SUPID offroad excursion i had. My truck got nice and warm. Since the winter has hit and i washed the radiator she doesnt get warmer then 160ish. Im thinkin it may have a low temp stat in it.
You could always get a grill cover to block air off. That would help it get warm in the winter!

 

Extreme high and low is what makes the block crack not 15 lbs of water pressure. Make sure you use your plug in in the winter and let it cool real good in the summer and dont hit water holes that may cool the block to fast.

 

Dunno about your block but shutting her down after a good warm up and that 1100$ iron monstrosity of a block is NICE and toasty for a long while afterwards.

How hot IS the block heater supposed to get. I had mine plugged in last night and it ended being like 36* today.... DAMN was the block HOT when i went to unplug it!! Im surprised i didnt find a HOBO camped under my hood... Or a neighborhood cat...

 

How many watts is the block heater, 500, 1000, or 1500? Higher the watts, hotter the coolant.

 

I flush the heater core on mine every year when it starts getting cold. You will be amazed at the junk that comes out of them. I also replaced my t stat this year. Noticed that I could drive like 20 miles and it would be like 150-160. Set for a minute and it would cool down to 140 with 40 degrees outside. Put a piece of cardboard in front of radiator and it warmed up quicker but still did not get warm. Replaced the t stat and warms up fine and plenty of heat in the cab.

 

I have no idea how many watts the heater is... Its OEM. I guess they ALL are. Its just weather or no they have the plug on them? Or so, thats what ive been told.

I need to flush my radiator AGAIN. After the head gasket blew and dumped 3 qts of oil into my coolant system... It looks like the Gulf in there!