I need a futon no longer than six feet?

Question

smaller is better

Answer 1

check out your local craigslist!

people sell them all the time on there, and you should be able to get one cheap

Answer 2

I think you're going to have real trouble finding one - all standard mattress lengths alone are more than 72".  Add the frame, and you're looking at at least 80";  take a look at the mattress chart from Woodshred.  You're futon would have to use a non-standard mattress length.