Making the swap isn't overly difficult, but I think that you're getting into more than you'll bargain for. You'll need a welder for sure, as you will have to put new spring perches on top of the rear axle, and ensure that the axle is square to the frame so you don't have any crab-walking while driving it. You'll also need to lengthen your rear driveshaft, you'll probably have to re-do your brake lines and much more. If you don't have a shop full of equipment, it will cost you more than a lift kit.
As for your front ride-height adjustment, you won't be able to crank up the torsion bars enough to make up for the 4+ inches of lift that you'll get out of a spring-over conversion (assuming you stayed with the original rear springs).
Unless you're considering making your S10 Blazer into a serious off-road machine (and forego any on-road handling that you have now), I wouldn't suggest this. I would suggest a lift kit instead - you'll be happier with the results.