Leonard,
I have a firewall mounted booster and brake pedal from a donor Cadillac.
When I got the truck there was stress fractures all around the booster mount on the firewall tin (it was mounted to just the firewall tin) wich I had to plate and beef up to support the booster when pressure applied.
Also the pedal arm had to be modified (cut sectioned welded) to clear the steering column .
So I would say that the bolt on in the frame rail type would be preferable in my opinion if the budget allows.
But for $ sake fabin a junk yard power booster to the firewall is not that big of a challenge just a bit of time,fabrication and add some support to the firewall tin and it works.
Photos of mine in my Bucket.
Tim
