I do not remember how my 53 was but most GM have the darn things located under the dash and are not fun to change. The last one was on my 2003 Silverado. You will need a manual to get to the darn things.The heater control valve on my '51 Special is stuck in the full heat position. (This is not good in the summer.) The cable is free but the control valve itself will not turn. I have not taken anything apart yet. Any suggestions on how to free it up?