yep.. you can grab a suitcase of cash and get a delco 10DN with a tach drive and external regulator.. OR.. you can just have your gen rebuilt at a rebuilder. OR you can buy a new replacement model.. I see alot of indian models... I got a spare one on the shelf from india.. I'd normally guess that it wasn't as good as oem.. but then oem was lucase.. so..

the indian one might be better.
seriously though... new gens for the 65+ models are easy to find and affordable.
Discount Tractor Parts and Manuals for Older and Antique Tractors System&r=mcats
a whopping 89$
Generator, 12 Volt - For models (2000, 3000, 4000, all after 1965 gas or DSL engines), (620, 8000 both 1968-75 with DSL engines), 9000 1968-1975 with DSL engine. (Part No: C9NN10000A)
or. swap your old pulley over and tach drive and pay 79$
Generator, Less Pulley & Tach Drive - New Generator 12V, 22 amp - 1965-75 2000, 3000, 4000, 5000, Gas and Diesel, (620, 622 1967-74), (7000 1971-75 w\ 4-256), 1968 All 8000, 9000 series (up to Dec\1969). INDUSTRIALS: 2110LCG, 3400, 3500, 3550, 4110LCG, 4400, 4500. LESS pulley & tach drive. Pulley is available (see p\n C5NF10196B). Tach Drive available (see part #C5NF17B282B). Replaces Lucas 22756. (Part No: C7NN10000C)
http://www.ytmag.com/store/parts/pics/wm_C7NN10000C.jpg
soundguy