Through the engine compartment. Process is described in the FSM and it seems easy (?): disconnect battery, heater hoses. Remove screws attaching heater housing to dash panel and remove housing and core as an assembly. Remove gasket to expose rivets (if used), remove heater core from housing. A note says that " core is held in position in the outer housing with plactic rivets; care should be used when pressing out these rivets" About antena: my '57 antena motor became more and more lazy these later weeks. Today it stops to work (as you expected with antena 1/2 raised ..). I'll remove it but does someone have already open the antena assy. ? I haven't any schematics or pics of the motor and i don't know if it's a motor problem or anything else in the antena. I've noted that the motor seems right because when i want to come down the antena the amperemeter goes to "Discharge" and the interior lights dimms.. Seems that something is freezing in the assy ! -- Philippe COURANT (Pau, France)- Webmaster des sites ACCF et C-I-F Imperial 57 Crown convertible Buick 58 Roadmaster sedan HT IMPORTANT: les messages "nouveau document microsoft word" contenant un "ver" ne proviennent pas de cette adresse mais d'un "usurpateur" (spoofing)... BEWARE: we never send messages "nouveau document microsoft word" with worm attached file ! Someone usurpates our identity (spoofing). Delete immediatly ! - American Car Club de France (ACCF) : http://www.accf.com - Chrysler Imperial France (C-I-F) : http://www.ifrance.com/c-i-f - Cadillac " Standard of Excellence " : http://www.ifrance.com/accf-cad - SportsCars : http://www.ifrance.com/accf-sprtcar