For many years, Wargames Research Group rules were the standard in miniature wargaming. The Wargames Rules: 1685 – 1845 cover the entire horse and musket period, and include useful army lists for Malburian and Seven-Years-War armies as well as the campaigns in India which preceded the Napoleonic Wars. I actually own a print copy of these.
Here are a set of rules from the man who is arguably the “Father” of American Wargaming, Jack Scruby: Basic Wargaming Rules.
Ross McFarlane’s 19th Century Square Brigadier rules are designed for late 19th Century wargames on a square gridded battlefield.
Wargames Rules 1685-1845 is a set of classic WRG rules from 1977. I own a copy, but you can get your own in pdf form at the link.
Ross Macfarlane offers Hearts of Tin, a set of simple Horse and Musket rules: