I have a 1970 Corvette 454-390 which was in need of a new accelerator cable and a kickdown switch for the TH400, what fun. First, REMOVE THE DRIVERS SEAT. I came up with an easy way of putting in the top bolt that holds the accelerator cable to the firewall inside the car on the top of the gas pedal. Simply take the threaded bolt place a nut on it, then grind a small flat at the very end of the bolt, using a center drill or a punch, either drill or punch a spot on the flat so you can drill a small hole in it. Once the hole is drilled remove the nut, this will thread the area where the hole was drilled, get a piece of string about 2 or 3 feet long, place one end through the drilled hole in the bolt (tie a knot) and tie the other end to a piece if thin welding rod or coat hanger (3 inches long or so), (whatever you have) now simply get contorted and squashed under the dash, push the accelerator cable through the firewall and line it up to the carb.,take the welding rod, place it through the cable bracket and push it into the engine compartment. Now get out from under the dash,stand up for a while, if you can, bend over the fender and pull the needle and string fairly tight, tie the end to something under the hood. This will allow you to get back under the dash using one hand and an open end wrench to tighten the bolt, this method centers the bolt perfectly and keeps tension on it which is easily tightened with an open end wrench once this is completed the other two 7/16 bolt that hold the gas pedal on are a snap. Using this procedure took me about 3 minutes to complete, I removed the bolt a couple times already and this saved me untold amounts of time. I hope this tip helps, it sure worked well for me.
Best Regards
Bob in Boca