Hi Rakkassan,
I have played lots of Michael Hopper's scenarios from his various sourcebooks, including:
Rise of Eagles: link
Eagles Over Bavaria: link
Duel of the Princes: link
Michael Hopper's scenarios are very easy to convert, because he gives strengths in terms of real soldiers, all units are assigned to brigades and/or divisions, plus the 'Shako' unit classifications are also very easy to translate into the terms used in your favourite rules (I don't use Shako either).
For 'big battle' rules like Blucher, Polemos Marechal d'Empire, Grande Armee, Volley & Bayonet, Age of Eagles, Napoleon's Battles and so on, it is just a matter of adding up the numbers in the individual units into appropriate 'brigade' sized groups.
For older school rules (General de Brigade, WRG 1685-1845, In the Grand Manner) then because the units have individual strengths, just divide by the figure ratio in your rules and you are done. Computer-moderated rules will just use the number of figures.
For newer rules (say Black Powder, Polemos Napoleonics etc.) that standardize unit sizes, you add up all the infantry then divide by the number of infantry units on both sides and then work out which units are average, small, large or whatever. Alternatively, then divide the total strength of each side by the average strength and then that gives the number of units each side has, e.g. if there are 10 French infantry battalions 500 strong and 5 Austrian battalions 1000 strong. The average battalion is therefore 750-strong, and each side gets 7 infantry units.
Is there a particular ruleset you had in mind to use?