When fresh, the typical Guajillo pepper is a wee bit bigger than a New Mexico pod type, about the same heat level as a New Mexico 6-4, and has a
very wonderful flavor all its own.
Since the recipe measures your peppers by pod, you could probably substitute 18 Guajillos for the 8 Anchos and 10 New Mexico peppers and have a sauce that won't taste exactly the same as Stormymater's sauce, but will be quite delicious nonetheless.
How
hot it is, depends somewhat on what kind of peppers went into the "3 tablespoons dried chili powder." If it's not hot enough for your liking, you can always spice it up easily enough with a little bit of bottled hot sauce, such as the well-known McIlhenney's Tabasco.
Around here, this import from Guadalajara is the hot sauce of choice for many Albuquerqueans, including me. I have no idea how available it is anywhere else:
http://www.hotsauce.com/Valentina-Ex...ce-p/1133v.htm