The pair will fight on the undercard of the Carl Frampton v Josh Warrington invoice in Manchester on 22.
Both fighters have seen their scheduled competitions pull out, using Jason Welborn vacating his name and JJ Metcalf with Williams because of trauma.
Williams formerly fought and conquer at Heffron’s brother Ronnie.
“It is going to be some struggle for me now on December 22 and it’s one I’m looking forward to as well,” Mark Heffron said.
“It is undoubtedly a bigger struggle than I’d lined up before and it’s one which will move me onto massive titles later. Charge for stepping up if nobody else wanted to and he is coming from light hearted to Williams. Give him his thanks for that.”
“One hundred percent it’s a bigger struggle than I’d lined up before – it’s a cracking fight,” Williams added.
“It gives me the chance to prove myself in the weight above too and I should say that I’m not being forced to move up since I can make light middle and will still make it”