In the late 50's the hanging pedal of choice were Fords , mid 50's, The reinforcing ribs on your firewall might cause interference, Today most builders want the firewall clean, minimal stuff visible. Things to look at , space available and the angle of the master cylinder, size of a power booster, outlet ports on M cyl. Bracing needed to keep firewall from flexing . pedal to floor clearance. pedal support to steering column and dash.On the last one we did, we added a 1/4 in thick back up plate about 6 X 16 inches to the firewall to minimize flexing. .