Update

The add for the transmission below was pulled by the owner, as was the obd1 intake, but the point was just the cost of the project. Less than a $1000 for the whole swap, if you do your own labor, and you're realy creative with the sourcing, and soo that might realy add up to more but not that much more. That is not much more than just getting a new m20...obviously.
Here is a, seemingly, high quality s52 for swap, with everything, but it's $3000.
97-99 BMW S52 with trans.

None the less, at $3000 it's half the price of a Metric Mechanic m20. So if you have an e30 with a blown engine, you could get an s52 installed professionaly for less than the engine alone from MM.

To be fair, Metric Mechanic's sport/rally m20 is 255hp so it is not any less than an s52. It is however $8700! For that much, you can have the above setup(treehouse bits, s52, obd1, installed) with a supercharger and be in the 350-400hp range.

again...Twin-Cam wins!