I'm not opposed to a turbo but its a lot of work for the minimal gains you are looking for.
I would look at a B&M or Weiand 144/142 roots supercharger. I have seen them used fairly cheap. I bought a polished B&M 144 in like new condition complete with all the brackets several years ago for $1250. You could run a big pulley and probably get 4-6 psi and improve your mpg by 1-2 if you aren't in it all the time and pick up 35-40 hp.
On my '89 GMC Jimmy, I used a Vortech s-trim kit that I got for $1500 used. I ran a big pulley and gave me 35hp at the rear wheels and picked up 2-3 mpg.
Turbo's are great if you have big money to build it right. However, unlike the supercharger kit, they aren't that easy to transfer from application to application and require custom piping, plumbing, etc. A small roots requires an intake change and pulleys and brackets.