David,

Some of the later 1800s used a B20 engine with fuel injection. This should give you the performance boost you are looking for. Later in the 1800 series, there were actually some cars with automatics. I remember reading someplace these cars used the BW35 transmission. Sounds reasonable since I believe that was the automatic tranny used in the 140 series at the time. The later 240 series initially used the BW55 tranny and its varients.

A little searching should find you a B20 fuel injected engine. The FI system is the early Bosch D-Jetronic. It gets its information from a manifold pressure sensor, as opposed to the more modern and more accurate air mass sensor. If a B20 with FI can't be found, then there is always the carb. version which your should be in a position to handle since that is what your car probably has.

The BW35 tranny should also be available with a little searching. You may find it already bolted to a B20 engine in a 140 series. Parts to rebuild this tranny should be readily available. You can have a shop do the work, or you can attempt it yourself if you are comfortable digging into one of these things. I have a Volvo green shop manual for my '82 1800ES, and I think it does describe the rebuild of a BW35. Can't tell you sure since the book is at home. Either way, unless the tranny has been rebuilt recently, I would consider rebuilding it in order to make sure the seals are good. It will save you grief later.

I think the real challenge will be getting the proper drive shaft, stick shift assembly, and linkage. Since the automatic version was not very common, I would think these parts will be difficlt to find. Maybe contacting one of the several 1800 parts dealers (such as Dan Thibauld at http://www.p1800.com/n_part.htm) will direct you to the parts. They should also be able to inform you of some of the issues of doing such a switch.

Good luck, and do what ever it takes to keep your classic going.