[Dave at Pelican Parts]

Bolt in? Uhh... There's bolting, and then there's bolting.

I think the 2.0 was supposed to return the best fuel economy of the stock engines--slightly more in the EPA tests than the 1.7, even! Not sure exactly why, though.

If you're serious about building for fuel efficiency, you're going to spend quite a bit of money and time and effort building up the engine. You can have a short-short stroke crank made (there's a discussion about this on the Shoptalk Forums Type 4um right now; someone needs to stay in a displacement-limited racing class) but it will cost big $$. Ditto having smaller cylinders made that still fit the case spigots and head registers. Smaller pistons are no big deal, up to a point.

I'd say just bolt in any of the stock motors and be done with it, myself. Or decide that you want the challenge of "max MPG" and get ready to spend a lot more money than you'll ever save on fuel.

--DD