Here is a good design, by Virgil Stamps K5OORhttp://www.hfprojects.com/projects.htm
Drive requirement: 1-2 watts RF (internal 3dB pad)
Power Output: 35 watts RF output (nominal) 160-10 meters; gain of approximately 15 dB
Spurious products: -40dB or better @ 35 watts
Harmonic content -45dB or better @ 35 watts
Filter Selection: manual 6-position rotary switch; 160, 80, 40, 30-20, 17-15, 12-10 meters.
A six-position Low-Pass Filter Module. The function of the module to attenuate harmonics from the transmitter to be below 40dbC on all HF bands, 160-10 meters. All of the parts including the rotary switch are mounted on a small circuit board.
Notice the number of torroids for filtering each band !