You done good!
Dear, ear, fear, gear, hear, near, rear, sear, tear
Bear, pear, tear, wear
Now that’s just cheating. 
This is nowhere near the longest, but I can’t resist its elegant simplicity…
read,read
brew,dew,few,grew,Jew,mew,new,pew…sew?
Nice one.
Mouth, south … uncouth
Touch, couch
bar, car, far, mar, par, star, tar…war, ear
Not to mention oar!
waive naive