Anything is possible...
Now, assuming we're talking about a Blazer here....
If I were to attempt such a conversion, I would track down a manual 4x4 Chevy truck of a similar vintage and pull all the goodies off it for the conversion. Finding all the gear boxes, brackets, pedals and other required drive train parts could prove to be very expensive and time consuming as well...
I think you'd also wind up with a 203(bad) or 205(good) transfer case, as I'm not sure they put the 208 behind a manual box. And be ready to do some crossmember swapping too. They'll almost certainly be different. Plus, after it's all said and done, be prepared to replace your driveshafts.
Me personally, I would shy away from it as it's a big and pricey job to do the swap (and I'm lazy and cheap
), there are already trucks on the street set up with a manual box that would be easier to just buy that way, and I'm not big on modifying MVs... but hey, that's just one man's opinion and you know what they say about opinions...