I am currently working on a 1997 Catera that is stock. Being unhappy with its peformance, I started looking for a good, reliable and inexpensive replacement engine. Yes, I would like an LS 1 but it is beyond my budget.
I bought a 1998 3800 Supercharged V6 from a Buick Regal on eBay for $500. I then realized I needed a front sump oilpan. A Holden Commodore, VT series, has a 3800 as the standard engine. A bought an oilpan of eBay for $70 including shipping. See the photos comparing it to a stock 3.0 Catera oilpan.
http://i251.photobucket.com/albums/g...e/100_0743.jpg http://i251.photobucket.com/albums/g...e/100_0740.jpg
See the oilpan installed on the engine:
http://i251.photobucket.com/albums/g...e/100_0738.jpg
In this configuration, you must use the rear most set of motor mounting holes which places it were the stock 3.0 sits.
http://i251.photobucket.com/albums/g...e/100_0739.jpg
The A/C compressor is in the same location as the stock 3.0, so minimal adapting.
The wiring is Holden VT as well as the ECU.