I think you have cover all the parts that need to be look at.
1. Cooling system, expansion tank, radiator, water pump, thermostat, fan clutch and Aux Fan
2. Control arms bushings, rear trailing arms bushings and Engine/Gearbox mountings.
3. Fuel pump, throttle body intake boots, sealing ring.
4. Crankcase vent system, vacuum tubing.
5. Alternator, a/c blower final stage resistor, pulleys and belts, starter, sub frame mounts.
Stay away from conversion to avoid headache unless you have a mechanic that have vast experience.
A M54B25 is reliable engine and they are also robust.
Take note an E46 is a relative old car and they tend to have a lot of issue if the previous owner never take care of it.
Once you taken care of all the wear and tears part, you are going to have a smile whenever you floor your ride.
