Yes the upper part of firewall protrudes in the engine compartment allowing for a more comfortable situated toe board and slightly more leg room. Steve
I built my first 32 pickups using 33 cabs (same firewall as 34) and there was slightly more leg room than my last 3 32's with stock firewalls. Also the 33/34 firewall allowed me room to tuck an AC evaporator up under the dash out of sight.
34 cabs have an extra reveal in the back panel.
It's very obvious when you compare the back panel on 32 & 33 cabs to 34 cabs.
The extra wide reveal allows the seat back to lay back slightly further for a more comfortable angle.
