I am welding up the holes in the firewall that I'm not going to need and I have two questions. The PO had removed everything from the firewall before I got the truck so I'm not sure what this plug is for, I think it's for the heater blower but I'm going to install an under the dash system so will I need this plug and the hole in the firewall? The photo is from a 66 panel truck but my 65 short fleet has the same hole.
Second, What are these two holes for and do I need them?
Thanks for the help