Problem with Power Disc Conversion

[Low69CST]

My truck came originally with non-power drums and i'm switching it to power discs. I got the bracket that bolts on the firewall with the pivots that hooks to the booster. The problem I have is the 2 levers that pin the booster rod and the pedel rod come all the way back and hit my freshly painted firewall. Its like the rod on the brake pedel isn't long enough. It doesn't even allow the brake pedel to rise all the way up to it's stop, the levers hit the firewall before the pedel returns all the way. I tried to adjust the pedel rod out, but ran out of threads. We had the same problem on my dad's 72 and he had a new and longer pedel rod made. Since this is the 2nd truck we did with this problem i figure we're doing somethin wrong.