Are you talking about fitting a Trap Special barrel to a standard K80? If so the answer is YES. The rib is on the barrel, not the receiver. You will probably have to make some adjustments to the stock, such as longer posts for an adjustable comb. If you are talking about changing the rib on an existing barrel, a call to the factory will give you the best information on feasibility and price.
To clarify my statement, you can not simply switch to the new high rib on your old unsingle barrel. You can fit the new barrel with the high rib to your existing receiver however. I answered your first question assuming you only wished to switch ribs.
I doubt if the factory will quote changing your old style unsingle to a trap special design. You would be far better off selling your existing barrel and buying a used or new trap special high rib barrel set. You might even be better off cost wise simply trading guns as the stock will have to be modified as well and if it's a combo set you have the additional cost of modifying that barrel set.