If I were to buy a 4 speed console for my 71 chevelle would it be possible to change the shifter cover plate on top to a 3 speed horseshoe shifter. Thank you.

The Hurst Dual Gate shifter?
This may be a bolt in:
http://go.mrgasket.com/ProductDetails.aspx?brandId=0&productID=22649&majID=800&minID=8002&selection=22&minselection=1

It is a Chevelle 4 speed console but it looks the same as a automatic just a different cover.

Absolutely, The consoles are identical all you have to do is bolt in the horseshoe shifter, and then put the automatic top plate on. Are you thinking of getting rid of the 4 speed? If so, are you going to sell the parts? Let me know if you are, I am thinking of converting mine to 4 speed

I was just offered a good deal on the 4 speed console, so I am thinking of putting it in my Chevelle and just changing the top plate.