1971 Twister

A nice 71 340 twister is coming up on auction. Are these considered rare or desirable? Haven't found much info about these cars. Does the Twister designation make any more rare or valuable than any other 340 Duster?
Being a mid-year introduction, the 1971's are fairly rare but I haven't seen production numbers on them. They have gone up some. Not as valuable as a true 340 Duster.