help with firewall holes

[JGross]

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

[jocko]

JGross, here's some pics that might help. These are from the firewall of a 66. In case you can't read the captions on the photos (they were hard to read in Paint) - here it is in a nutshell:

Connector near the heater - is not the heater connection - I believe it's the primary wiring - the wires from the connector come through the firewall into the engine compartment, Tee just behind the vacuum advance canister. One section then goes to the starter solenoid, then the other section goes to coil (+) and also to the temp sender unit on the intake manifold. (the second yellow pointing line points to the heater connection - it's just barely visible at the bottom of your picture - but I'm pointing to it in mine - the rubber grommet with the orange wire coming through it).

As for the other two holes you ask about that are more on the driver's side, they both feed into the rear light harness (you can actually see that they connect (red line) below and the ribbon all goes down the inside of the frame rail to the tail lights.

Bottom line - might want to plan to use the firewall plugs (especially the one near the heater) unless you're rewiring the whole truck in a custom fashion and will have different points of crossing the firewall. If stock wiring, I'd definitely plan to use all of these.

Hope that helps.
Jocko

[jocko]

a little more detail - the 2 red circles represent your firewall connector near the heater (plug shown twice for each side of the firewall). This shows you all that they connect to - i.e. starter, coil, temp sender, etc.
jocko

[ranger374]

doing the same thing myself on a 62 cab. I talked to my grandfather (who has built numerous street rods) and he told me that he usually welded them all up and just re-drilled new ones where he needed them as needed. THe only ones i left on mine were the ones for the heater bolts and hoses, and the brake push rod hole for the master cylinder and attatching bolts--3 i believe.

I will put in a universal wiring harness, and probabally just use 1 hole (i hope). I will also have to drill a hole for the clutch linkage since i am using a 63 frame and a 63 clutch pedal which was swapped out with the 62 clutch pedal.

[Chevy Fleetside]

That is what I did. I am going to run the wires out of sight. I am also running the battery back behind the cab so I did up the inner fender to get ride of the Trangular indent.