Alright, you need a new motor and a tranny... im not very sure on the 4x4 part but im thinking it will still work with a stock tranny... or u might have to get a diffrent style tranny for the 4x4. I have a Chevy Vortec 4.3L V-6 and matching tranny that I might possible sell .. I wouldnt go with the V-8 in the blazer, its a little to much power unless you are towing or swamping... You might feel the need to go a lil fast and flip that baby if you know what I mean. Oh yeah, if you go with the V-8 then you might have to do a little bit of work with the firewall unless you are having it done by a pro. Take time and think wisely....