Firewall Flex From Clutch

[tpull123]

During my swap, I am getting quite a bit of firewall flex.   TO give some details, its a 94 Ford mastercylinder.   The cab was an auto, but drilled the holes out to mount in stock location of the 86 chevy cab.   Did the manual cabs have extra bracing there that I am not aware of?   Or does anyone make an aftermarket brace to install?   Clutch is working awesome, just not sure how long it would last with the way its flexing.

[1980c10]

I posted a pic of two types of clutch pedal assemblies
The set on the left is from an '85+ with a hydraulic clutch set up.
The pic on the right is from a mechanical set up.
With the hydraulic set up you can see the two rods they bolt up against the cab and clutch cylinder(uses the same bolts) and provide the extra support to the firewall. I you do not have this set up it is likely what you'll need to get.

[tpull123]

And hence there is my problem!!   I used the clutch pedal assembly out of a 78 parts truck I had which had the clutch.    I modified pedal to work, but did not know about the extra two braces. 

Thanks for the info!!    Really wish I had a complete truck to reference, would save me a lot of time in little issues like this.