The needles are important. The manual will tell you which goes front and back. As for pilot jetting, IF the floats are set correctly and there are no other issues with any part of the carb, then yes, replace with #40s and reset the A?Fs to 2.25 to start with and adjust for correct idle charge. I did that by smell. As for the mains you can do it with the plug tests but it will take more then just a few minutes of running to tell. You must become..."One With Your Brute". Being lean or rich has many different sounds, feels, smells and running nuances that need to be read along with just the plug. That or..have someone do it with an A/F ratio equipment.