I owned an ART II for several years. I liked it, especially on my M1A. I wish I still had it, but for what I had in it along with the hard case I'm glad I sold it. I might buy another one, but from everything I've seen the latest models are not of the same quality as the old milsurp I had.
Not bad, mind you, but not the same.
http://www.leatherwoodoptics.com/
SWFA carries them, also
www.swfa.com
Sure, there are newer toys on the shelf. Some things just seem to keep working fine, despite their age. For my money, you find something you like and can become proficient with, then you stick with it. The ART II was the first mildot scope I owned and I learned a lot about how things work and why.
The Leupold is probably a better optical quality scope than a new production Leatherwood, but since you don't state the specific model Leupold, I can't state an opinion.
I'd be more inclined to put a scope other than a Leatherwood on your Enfield, simply because of the way the externally adjustable ballistic cam and cradle on the ART must be attached. It's simpl, but not as simple as you think.
Don't get me wrong, I like the Leatherwoods. I submit that you would be better served by a more conventional scope of equal or better quality.
Regards,
Rabbit.