You must ask yourself, do I really need a low-pass filter?
Tube amplifiers have a Pi-L output network, which inherently reduces harmonic output to antenna. You should never need a low pass filter with any decent tube amp.
Solid state amps do need output filtering, for base-station use.
Those amps built for this purpose already have this.
Only case I could see without filter is home brew, or a CB pill amp which is a total pain to power as a base.
But even if you put out harmonics, the VHF low band TV 54-88MHz is largely vacated due to digital TV migration. It would be surprising if you had a TV station your harmonics could actually trash, considering how few there are on the air. And those that are on, are digital. so how would neighbor know?
Harmonic problem on some other frequency band?