Need to replace the '74 LeSabre's heater core, which looks like it's going to be tough, with the dreaded task taking place underneath the dash according to the shop manual, and not the typical 8 bolts and out from the firewall in the engine bay. "Just four bolts" after disconnecting the temperature and defroster control cables and the vacuum line to the diverter door actuator diaphragm. Pictures of shop manual attached. Anyone had to do this on a similar vintage B/C/E body big car and can offer advice / hacks? Nothing found on YouTube. Any suggestions or pointers appreciated. Thanks guys.