Early A with 360/power brakes

First off, there is zero difference in deck height between a 360 and a 273 and the valve covers are maybe 1/4" taller at most. What year brackets and linkage did you use? If they are not '66 or older they will not fit properly. The problem is that early A's were designed to accept a slant six, period. A V8 is a shoehorn job and there just isn't room in the engine bay for a lot of useless frippery. As mentioned before power brakes are not needed if the master cylinder is sized properly, especially in a 2700 pound car. Before you go to the expense and hassle of trying hydroboost or a smaller vacuum booster, try a master cylinder from a '74 Charger with manual disc brakes. It has a 7/8" bore and if you never saw it on the firewall you would swear the car had power brakes. It's the only one I use for my cars and is available at any parts store for around 30 bucks. I don't like the stock "standing on a rock" manual masters either. That's why I bolt up the Charger cylinder every chance I get. Good luck.