my mill is knee driven, has about 15" of z travel, the spindle can be used free for tapping. it was built by cnc automation inc of amherst nh and they still make them. it is driven by their own cnc control software not mach3. mine worked well for 10 years, but have had issues with replacing old computer parts for the last 3 or 4 years, its running fine now with the help of a friend more legacy computer savvy than i. im sure they use newer computers now. never any issues driving the knee. their control software works fine, tho i wish i could switch to mach3 myself. but the "motion control" board in there is unlabeled, a mystery to me, and they dont provide any help with this older machine, they want me to upgrade to the newer control. i guess i would say if you chose to deal with them, their support was great for the 1st 5-6 years, then i was invisible to them. if you were willing to help him with just the mach3 and pc part, this might be a good start:
http://www.cncmasters.com/index.php?page=cnc-supra-vertical-knee-mill. it is however, z spindle driven not knee driven. mine is based on the 10 x 54 acra and it has held up well for me.