I am trying to restore the heating and A/C on my 1978 Aspen Super Coupe. I decided to purchase a new evaporator. The original evap coil had grooves in the rectangular block for O-rings (2). The replacement is a flat block with no O-ring grooves. I do not understand how this is to seal. I also have a new expansion valve with several O-rings and flat gaskets with no mention where they go. Anyone with insight?