In my 1980 camper I have had
1) stock aircooled motor 
2) 1.6 Turbo Diesel 
3) 1.8l gas (1989 jetta)inline4 w/Digifant 
And soon 
4) 2.0l gas (1995 jetta)  OBD-I or -II motronic (have both options) 

I took my stock aircooled motor on 2 3~4hr trips and it was brutal and slow
I took my 1.6TD NY to FL and it was nice and smooth albeit noisey but 27mpg till overheated by bad belt
I have taken my 1.8l digifant engine all over creation, NY to FL & back to NH Mtns and it's good but with the aircooled trans I'm looking for that little more HP/TQ of the 2.0l engine.

The parts aren't hard and you can do it in stages if you like. 

There are some threads on www.thesamba.com/vw in the vanagon forum on aircooled swaps. 
You do need the special coolant and Diesel Vanagon bits, but they're available. 
My recommendation would be a KEP adapter then add the Diesel motor mounts & oilpan/pump 
That'll give a bigger clutch, a cheaper starter option (keep your old one) and really costs similar to the Diesel Bellhousing/flywheel/clutch_disc/pressure plate

Feel free to Pmail me anytime for more information. I've done and drive a few of these.
I feel the aircooled vans ar the best rust free bang for buck, and upgrading to watercooled isn't much more work than the maintenance items a H2o van has to go through at some time in it's life anyways. 

Dan in Syracuse, NY 
www.vwccny.com 
---------------------------------

Date:    Tue, 6 Mar 2012 18:07:52 -0500
From:    "Mr.mds" <mds_1976@HOTMAIL.COM>
Subject: 81 Air cooled... Engine conversion options??

Hello to all who read...

My 81 is knocking badly.. And I am considering a conversion replacement.=20 Was just wondering which way to go, I'm looking for the most cost effective (= not cheaping out) solution..  Any advice would greatly be appreciated!

Thanks for reading!

MS=