The reason that Chev V8 engines have been so popular in hotrods over the years is not because they are better than Ford V8 engines, (although some would argue that). As J Robinson points out, its far more a matter of size. To run a stock Chev V8 in a model A with a stock length hood, you will need a 4" recess in the firewall. Ford engines are between 3 and 4" longer than a Chev engine, so either you have to stretch the frame and run a non stock length hood, or move the radiator shell foreward 3 or 4" and run a non stock length hood, or live with a 7" recess in your firewall, which puts your knees up around your ears!!! Ford has caught on to this failing in the last few years, and offer a bunch of super short water pumps and pulleys and front cover, but they coast well over $1000 to buy as "aftermarket" peices.
Another major issue with running Ford V8's, (at least in the past) was that Ford motors had a front sump oil pan, and the sump was exactly where the tie rod and possibly the drag link (if you had cross steering) wanted to be. This problem has been alleviated somewhat by the famous Bronco rear sump oil pan, but for many, many years, if you ran a Ford V8 you had to drop the tie rods to clear the oil pan. Chev has always had a rear sump oilpan, right from the factory. So----hotrodders being what they are, and not wanting to buy any more work than was absolutely necessary, adopted the chev V8 as their darling.---Brian