I came across this eHow article on swapping a SR20 into a 240SX. There are plenty of forum posts showing how to complete the same swap but this is nicely concise and I figured you can never have enough information.
Here is a nice RB25 powered 1989 240SX for sale in Illinois. The owner claims the car makes 411 horsepower to the wheels on 17 psi of boost. Owner is looking for $10,000 OBO. Source: NoRotors
A member on LS1Tech forums posted the weight measurements of a KA24DE 240SX and a LS1 swapped 240SX. The LS1 240SX weighed about 19 pounds more then the factory setup. Source: LS1Tech
This S15, named Sublime, has a turbocharged three rotor Mazda 20B. The large turbo is a GT47R and helps the engine produce 705 horsepower. The transmission is a Supra R154 five speed. The project took three years and $90,000. If anyone else knows more please comment. Source: Autoholics and Free Style Rides
If have been wanting to swap a V8 into your 1st or 2nd generation 240SX you are in luck. A member on Zilvia.net is selling a complete kit to swap a V8 into your 240SX for $2K OBO. The member lives in California. Source: Zilvia
This 1989 240SX has a LS1 swap. The engine is making 380 horsepower and the car only weighs 2,300 pounds. Source: LS1Tech