Not just saying this because it's the SD forum, but honestly one of the best distortion pedals I've used for a while now through an ultra-clean amp has been the SD Diamondhead pedal.
Really fat and full sounding without getting too harsh or mushy, and has a great sounding boost function on there as well. I've used it to good effect with everything from 70s hard rock on to more extreme stuff like doom/death metal even. I'm kind of surprised this pedal seems to be overlooked so often, honestly.
Aside from that, another pedal that I've used successfully with clean Fender amps is the Wampler Sovereign, nice articulate and not mushy sounding pedal with a variety of settings capabilities.
Not quite as versatile for my needs as the Diamondhead but close.