The caps over the mixtures screws are easy to remove. I use a fine hacksaw blade and "notch" the bottom of the throttle body slightly on either side of them, then drive them out with a punch smacking them forward and breaking out the "notched" area at the same time.
At most I'd consider going one size larger on main jetting, for the stock 454. This new fuel has less energy, and it helps to put more of it in there to keep the engine happy. I'd leave the rest of the carb stock, other than upgrading it with one of our kits.....Cliff