my '68 elcam w/ A/C needs a new heater core. ive done a heater core before only it was worse ('89 Volvo 780 Bertone). i will have no problem completing this job once i get this answered: do i go in from the firewall (remove A/C assembly and stuff), go at it from under the dash of the pasenger side, or both. if you cant answer questions good please point out someone who can. thanks a bunch.