I have recently found a superb website which provides massive
amounts of information on the Spanish Army :
http://www.aulamilitar.com/ (http://www.aulamilitar.com/)
I was particularly impressed by inclusion of the 'Estado Militar' for
both 1805 and 1755 (essentially, a pictorial reference for every
Regiment serving in those years).
It also includes a regimental listing for every year between 1717
and 1973.
Just in case this is of interest.
Phil