20 inch wheels

[Lo78]

I have done some searching with no luck. Not sure if im searching right becouse you would think id find these answers. I have a 78 swb with a 5/7/drop, i have 20s and im wondering on what tire to get. I went to discount tire and they said a 275/45/20 would work great all the way around. he quoted me a price of 629.00 out the door for goodyear eagle gt2. Does this sound like a good price and the right size. thanks steve ( oh the backspace is what ever comes off the shelf with the wheel )