I have a 03 Safari with the 4.3. I had a 00 Jimmy with the 4.3. Don't get me wrong, it's not a bad motor, but there won't be much of a signicant gain if any over the amazingly simple inline. You won't get better gas mileage, just the smog control maybe. Btw the van gets 13 mpg and the Jimmy got 15 - 17.
To save money, a 350 with tall gears would get as good or better mileage AND have a lot more power. Better yet and way more cool would be a hopped up inline 235, 261, 250, 292 or 302 with the proper tranny, tires and gearing. Just my extremely biased opinion.
