buy the cheapest, crustiest cylinder you can find,( this will set you in the owner tank catagory ) take it in, tell em you want to go the next size up ( or whatever size you desire ), they will charge a "upgrade" fee. about 20 bucks or so depending on the size jump.
exchanges here are about 16.00 here for 25/75 on a 80 tank
and yes, they recertify old cylinders within spec.