Which kit/heat-AC box did you use from them?

This is a non air car.

have you contacted them and asked ? I don't think anyone makes a kit for that application other than a hang under the dash unit but I could be wrong

Yes, I have, which is why I’m on here…they said to measure the area under the dash and look at the measurements of some of their universal units on their site…problem is there is no dash in my car at the moment and I’d like to get it installed before the dash is painted and reinstalled.

I used the generic classic auto air one for hotrods in my 65 coronet.
since mine was a non-ac car, nothing poked through the firewall.
I created a plate that bolted to the firewall and then bolted their a/c unit to that plate.
that way I didn't have to drill new holes in the firewall.
I looked at vintage air systems, and see they are very similar.
mostly I didn't have space issues because I could shift the airbox mount.
But I found I did screw up in that the classic box had forward facing vents for defrost and I didn't put any spacers in, so I was too close to the firewall to mount the tubing on that side.
I think they only thing that might be in your way is the fresh air vent on the passenger side.

I would measure how much room you have from any bracket holes for the upper area the dash mounts to just before the firewall curves to the floor for top to bottom. then where the fresh air vent is to where the ash tray is, assuming your 63 is similar to a 65.
they have changed there stuff a bunch since I bought mine, but I used their universal kit at the time. which looks like the street rod kit now.
The custom cooler looks like it would be easier to route the vent tubes, but no idea on the size difference.

Thank you

IIRC, my '63 dash had less room behind it than my '64 & '65 did.
I could be wrong, as the cowls also changed from '62-'63 to '64-'65, but it's certainly worth checking.
I suggest the OP sit his dash in place and take a few measurements.

i would strongly encourage you to put the dash back in temporarily, take your measurements, Trial fit / install / mount the unit and then proceed wit the build. Doing it the other way is rolling the dice. It it much easier to make and correct a mistake NOW then during final assembly.

the other option of course is one on the slimline under dash units. Keep us posted

One option is you can order this mock-up version of the Gen IV to test fit it in place of the original heater unit in your '63 before ordering the actual evaporator. I used the Gen IV in my '68 Barracuda convertible and bought the underhood stuff from Nostalgic AC Parts in Florida. I used a much larger condenser than Vintage offered.

https://www.vintageair.com/custom/product-pop.php?pn=671450

https://nostalgicac.com/

Don't forget to insulate as much of the interior as you can while you have it apart. Dynamat dampens the panel resonation, but its the double-sided, foil-covered jute mat and aluminum foil duct tape combo that really stops the heat, sound and fumes from passing into the passenger compartment. Grab that from Speedway Motors.

https://www.speedwaymotors.com/Aluminized-Heat-and-Noise-Insulation-Shield-Double-Sided,32193.html

there are super small ac/heat units available to fit street rods [think 33/34 ford] that might be something to consider.
however, you will do yourself a favor by temporarily re-installing your dash to get some critical measurements of the available space you have.
don't forget the wiper arm space needed. [i can't remember if the 62-64's had the arm mechanism under the dash or not. [sorry, "old timer's disease" caused by lots of spiders filling my old noggin with cobwebs. ]