In the picture, there is two visible openings for the stock AC/Heater box. NOw that I'm installing a Non-AC heater box, do i need to do anything with the hole on the right side?, or can i just put the new box over it....would it be a good idea to block it off with a metal or plasic plate since it will serve no function? (at least i don't think it does anything, maybe i'm wrong)

where would the air that the fan blows come from?

Well, it appears (from looking at the Heater Box) that the round hole on the left is where the air gets pushed into and out the heater vents inside the car, but maybe I'm wrong...i really don't know for certain...can anyone tell me what both holes do?

i'm having same problem, except my holes will be patched forever. Get some sheet metal, or diamond plate from ACE, cut it to fit, bolt it on and seal it with RTV.

so I'm assuming that i can do that with just the square shaped opening on the right side, i would still need the circular hole on the left for heat...i think the hole on the right was for the air condenser which is gone now...

Put the heater box on w/o blocking anything. The round one is the intake for teh fan. The rectangular one is the supply that leads to the heater core and ducts in the dash. Block either and your car will be rather chilly in the winter

Not to step on anyones toes but the round one on left IS where the
blower motor mounts. The rectangle or square on right is where A/C
unit comes into play and you can block that one off.

Why block off a hole you won't see- especially if you don't know how the system works?

I was always under the impression that one is an input, the other an output. Air flows through the box.

well, the A/C Unit sits (sat) right in front of the rectangle/square type hole on the firewall...but I don't know if it also serves as a function for the heat...if it does, then I will need to leave it alone and just install the Non-AC Heater box, if it was in fact just for the A/C, then i can't see why blocking it off would be a problem...but i guess I'll just leave it alone and install the heater box. I'll let you guys know if it works correctly, but I'm guessing that it will

The heater core is on the hole! Look cant you see it?! Just put the box on, dont block it.