is it a 3.3L or just the 3.0 or what is it? is it fast... just go all out

The engine is a 3.2 something motor. Its the most reliable engine BMW has ever made along with the 3.4 motor. However BMW ruined the design when they started selling the last 3.5's with a 10 to one compression motor.(still a good motor but not as bullet proof) Its known as the BIG 6. The 535 used a 3.4 something motor with just 1 HP more and 12 ft Lbs of torque. The 533 uses the early motronic system and the 535 uses the more fuel efficient motronic system. The cars are extremely reliable with minimal repairs needed compared to the new BMWs of today. Always get one with a 5 speed if your looking for a fun fast ride. The 533 your looking at have very few bad common problems.
If your looking to buy that I suggest you put in a updated engine management system using the 1988 735i system really goes in nice. It will work with the 3.3 motor. If you do that the car will get 4 to 5 more MPG and run better.

Before buying check the trunk they like to leak. Watch the gages make sure they first work and second the needles don't jump around. Check the brakes hydralic power booster for leaking a little is OK and bunch is not. If you hear any valve noise above slight tapping stay away from it, no valve adjustment will make it go away. When taking off from a stop look for a slight shake from 1 to 5MPH. If the car pulls or drives funny stay be aware an aligment might not fix the problem it may have a twisted cross member. Check the wires that go to the doors for wear. When the car is off step on the brake petal many times it should take 20 or 30 presses before the petal gets stiff from no more power assist in reserve.
Most of thoes things I just said cover most of the high cost repairs. Other than that a basic check from any tech will tell you the rest of the overall condition.