Hey there, I'm generally a forum creeper, butttttt, i'm going threw the same exact situation as you. and typically its harder then hell to find turbos and such for the earlies.
But if i were you, i'd get ahold of clay over at riffraff diesels. shoot him an email and he'll tell you everything you wanna know. he told me straight up, $25 bucks shipping both ways and that it'd be a whole lot cheaper to do it myself, seeing its not such a hard task to do.
The early turbo kits arn't listed on his web page, but they do have them. Either way, its a top notch outfit and you could honest to god rebuild about 12 turbos for the price of a new one (including the wheel).
The life expectancy on rebuilds are pretty much just short, if not as long as new ones, depending on how the housing looks, how clean the air coming into it is, how hard you push it, ect.. as long as its done right.
The reason your not finding any for the earlies is they completely changed the plumbing on them and the newer ones have a totally different pedestal. That being said, there moreless rarer then the 99.5-03's. only half a year of production means Less target sales which in turn means less production.
The only new drop in one i can think of is from bean, and even its a rebuld. i'm thinking the aurora series may be coming out with a new one, however it may just be a 99.5<
Beans Diesel Performance - Early 1999 Power Stroke BDP Dominator 66 Turbo (Powered by CubeCart)
On a second note, they do produce kits to turn your early into a latter if you so choose, only problem is it actually costs a little more then an actual rebuilt turbo you can find on ebay.
Hope i helped at least a bit, best reguards,