There were tons of vehicles where the 2.0L and V6 engines were options depending on the model.
The V6 is only 3 cylinders on each bank.... so it's just as compact as the 4 cylinder engine.... might actually be slightly shorter.
The Opel Omega ( Cadillac Catera ) was rear wheel drive.... but that whole generation of V6 engines 2.5L to 3.2L would fit on the Aveo gearbox.
here is a picture of a 3.0L Catera engine
http://cgi.ebay.com/ebaymotors/CADILLAC ... _569wt_939Oh...... how about this one that I forgot to mention.......many of the Saab engines also work with the F16/F20 gearbox..... so it's possible to drop in a Saab engine as well.