Smooth firewall question

[FrankenChevy]

I'm about done with smoothing the firewall on a '67 Camaro. I've butt-welded panels in the a/c hole(s) and I started to worry that I just might weld one up that I'll eventually need (not too big a deal...just more of a pain in the rear than anything). I plan on putting in an aftermarket a/c (Vintage Air or something similar). I've attached a pic with the holes in question numbered. I know that I will eventually have to drill some holes for the bulkhead fittings but I want to locate and drill these later when I get a better feel for where I would like them. I think all the holes numbered (1 thru 5) need welded up along with all of the holes remaining in the outer righthand cowl. Is this correct? Any help is appreciated.

[MrQuick]

4 is for the AC harness, ...i believe 3 & 5 are holes for the box stud or firewall pad push pins. The others im not sure of. If you are going with an aftermarket AC system just fill all the holes and drill where you need them.

[68ls1wannabe]

So will it be fine to finish the firewall and paint it then come back a put the aftermarket a/c in later? I hope so because that's about where I'm at now.

[6'9"Witha69]

1 and 2 are the old heater hose holes (say that 5 times fast). I am going to weld all but #4 on mine since I still use it to run a few wires throught the firewall. If you don't need it there for that, fill 'em all!

If you are going to use the Gen II compac or similar system them drilling later is fine as you can place the bulkhead behind where the fender covers it up. I use an older VA replacement system so I kept the big rectangular hole in the firewall (you already filled it).

[FrankenChevy]

Thanks for the feedback. I just filled them all this morning so now it's just a matter of putting new holes back where I need them. After all of this, the firewall is not as flat as I would've hoped after filling the holes. This is primarily due to panels not aligning. I was able to keep warping due to welding down by working slowly and letting it cool but I couldn't get everything to line up in a plane. I knew this was a problem before filling the holes. I've replaced the complete firewall area (upper and outer cowls, firewall, and upper dash) with aftermarket parts so I did the best I could (i.e. pulled, tugged, beat, etc) but the panels did not fit properly (or the 40 year old car was off). I even had to split the new firewall down the middle and take out a 1/4" wedge to get it to fit since the center to center distance on the subframe mounts did not match-up. I guess I'll have to go with a second plate welded on the firewall unless the future bodyman can make this work (without tons of filler). I've read the posts on this subject and it seems that putting filler on this thin of metal can lead to cracking (definitely makes sense). I was wondering if this secondary panel might be a good candidate for bonding on using structural adhesives (after I hammer it more flat than it is currently)? Not sure how I would address the edge treatment (transition to the adjacent panels) but the center could be held with these adhesives. Any thoughts on this idea or has anyone done something like this? I've even thought of bonding on a thin, flat piece of carbon fiber in this area. Not sure if this will look good or not. I'm looking for the resto-mod/PT look without venturing into the import-look. I also have the same problem with the edge treatment on a bonded CF panel.