Planning to get a van next year. I was thinking a quigley 3500 passenger van, but not sure what kind of a mpg hit I'd take from the 6.6. Anyone have any ideas?

 

to add a bit more information. I was to vacation with my family of 6. We've outgrown the minivan for long trips.. I'd also like to be able to do a bit of towing, maybe a small rv trailer for the camping trips through the rockies,, but also the occasional heavier load closer to home. The 6.6would seem the better choice, over the 4.3, but if there is a huge hit to the wallet driving it,, we may end up not using it like I want to.. I've already got 1 fuel hog I try not to drive more than 5 miles, my v10 excursion.
the other major contender would be a transit 1 ton AWD ecoboost.i expect it would tow a small TT as well as a 4.3, probably better in the mountains, but is rated for far less.

 

So I had a 1991 with a 5.7 and it was a pretty consistent 15 whether I did 65 or 75. Right now I have a 1994 with a 4.3 and it does not have the torque of the 5.7. Particularly on hills I have to be on the gas harder and it gets worse fuel economy. Everything else is more or less the same, except the 91 was a conversion and both weighed more and had the high top.

Now that hardly compares to the current trucks, the modern 4.3 is much more powerful, but if you're going up grades you will probably still want the torque of the 6.6. Particularly with a trailer.

Unfortunately these are exempt from the Fed fuel standards so I don't know you can look up what sort of economy they're rated for.