I have tried to replace my heater core in a 1965 Dynamic 88 Holiday. There is on Bolt/nut I cannot reach, I was stupid and drill a hole in the fender well and still could not get it. Any known trades (trick of the trades) to do this.
Thanks Dean

 

Do you have air conditioning? Sounds like you do not.

Last time I replaced my heater core, I had to lay on the windshield inverted and twist my arm to get at the bolt.

You could also remove the right fender and hood to gain access.