How close is A/C and heater core to firewall inside? Want to drill into firewall

[Cudakiller70]

1971 Challenger 340 factory A/C car. I want to drill a couple of holes to mount my coil onto the firewall inside the engine bay, but I'm afraid of drilling into the A/C heater components behind. How much room is there? Is this a no-go zone?

[Cuda Cody]

With a heater box there is about 1/2" of insulation.  But not sure on an AC box. 

[Cudakiller70]

Oh boy that's tight 1/2"

[Cuda Cody]

There's a few options to use to stop a drill from going to far so a 1/2" should be plenty. Just have to be a little careful and take you time.  Also, can you put it up higher so it's not in front of the ac box?

[Cudakiller70]

Of course I'm wanting to mount it just under the heater hose outlets Do you think with a stop on the drill bit it's possible?

[anlauto]

If you stay more to the right under the AC lines you should be okay. You may hit the box, but nothing vital 

[1 Wild R/T]

Through the years I've mounted a few coils on the firewall or inner fenders, later I always wind up regretting it & wind up welding up more holes.... These days I'd either make up buy a bracket to mount the coil off the engine...  Maybe something like this....

http://arengineering.com/products/vertical-mount-single-bolt/

[Cudakiller70]

Thanks all for your help