Heater Core Mounting

Is there a foam or rubber surround of some sort that goes around the heater core in it's enclosure? If so, any idea where I can get one or perhaps pictures so I can make one?
I'm foolishly installing all the factory heater parts my uncle removed 30 years back, it can't be worse than no heater (or so I think).

 

It might not matter in California, but this will improve the stock heater's output-
"Placebo" heater upgrade

 

I’ve seen a mastic type sealing tape between the heater core box and firewall on several Jeeps. Similar to what was used between the fenders and tub.

 

I just rebuilt my whole heater core assembly and boxes with the motor and all. My core was held down in its box with two 1/4" wide U shaped straps that screw down in each corner. Under the straps was 4 pieces of thick rubber material that held the core in place. My core had nothing under it. I cut some more rubber out of two black rubber bungy cords and placed them under the straps and between heater core. Sand blasted all boxes , replaced two speed motor, primed and painted everything inside and out with black semigloss spray paint. I even took the deflector damper that deflects air to the floor or to the defroster vents and replaced the felt around the edges. Felt was 1'4" felt from Grainger. My boxes were mounted on firewall with no sealant, but I might consider that when reinstalling. You can see the straps in upper corner of picture. You might have the core checked to make sure it doesn't leak.

 

I've used neoprene (wetsuit) material to pack on the two sides where the core meets the outer box. I've also used the same material, only about 1/8" thick, on the flap to make a better seal. You should have a few surf shops in town that should have neoprene scraps. I remender pretty good surfing at Steamers.
I acually get some good flow inside in the "fresh air" position when the 4" hose is connected to the grill scoop.
-Donny

 

Ah, knowing there were metal hoops that held the core to the upper box and some clue as to their shape was the key bit of information I needed.
Thanks! I found my pair in a box of kept parts and they fit my core snugly. The original screws are long gone sadly, but I'll manage.