Finally getting a 72...

[SeventyOne]

I wouldn't worry about the blocks or the ubolt on the rear. Blocks get a bad wrap (lol) because of axle wrap and they're the cheaper way to lift the rear.

Assuming the truck is mechanically sound the 4hr ride back on the freeway will be no big deal just watch for steering wander. The 3spd probably won't put you at a nice RPM at highway speed but you'll be fine - I would probably keep it at 55 tops just since its really your first shake down of the rig.

Stock axles are ok for 36" tires IF you don't wheel it (or wheel it on mild trails). Others might say 35"s max...

Things to look for buying a blazer:
rocker panels, cab floors, rocker box, fiberglass top/hatch condition, body mounts, plus a lot of other crap

Good luck and have fun!