[mr48chev]

I'm an under the floor guy because they are just too ugly to be in the engine compartment with the engine you spent all that tme and money detailing. I've spent almost as much on finned and polished cast aluminum for my 292 as I had in the truck when I drove it to the 1973 Street rod nationals in Tulsa from McGregor Tx. Plus I have a pretty big 4 barrel intake going on it. Add in that I want people who aren't totally in the know on Chevy sixes to think and maybe argue that the truck has a hopped up 216 or 235 or even 261 than the 292 when they walk up and look at the engine that will be as close to factory gray as I can get with the polished aluminum. I don't want them looking around a street rod style booster and master cylinder. It's all about what I want others to see when the hood is open.
Add in that I am running a cast iron V8 bellhousing on the original crossmember with an AX 15 behind it. stock floor pedals simplify the clutch linkage as I already have all of it. I'll most likely run a hydro vac rather than a vacuum booster.

Function wise they work great on the firewall as long as you properly reinforce the firewall so you don't crack it out. I had a large square piece of 3/16 or so plate that was maybe 12x12 or larger sandwiched between the pedal assembly and the firewall on the inside to spread the pressure out over a large area when I ran the booster and master cylinder on the firewall. It's simple and it works, works best with an automatic rather than a stick as you don't have to figure out a clutch linkage setup. In truth the firewall mounted unit is a lot simpler if you are running an automatic and aren't concerned about the booster and master cylinder blocking folks view of the engine or aren't concerned about having a perod correct for your build plans engine compartment.