lokar pedal assembly question

[dhunt00c]

I have a 68 C-10 cab, firewall holes have all been filled.
I've noticed there is a different locker pedal assembly for 67-70 and 71-72.
The 71-72 seems to be a cleaner install as there is no outer plate on the firewall.

My question, is why are they built slightly different? Anyone know if its because of factor firewall holes or to correct an alignment issues with the carb?

I like to install of the 71-72, but i don't want to order it if it's going to cause me headaches. Anyone have knowledge or experience here?

Thanks in advance!
David