Williamson gave his career a much-needed boost by halting a three-fight losing streak when stopping Mark Dickinson for the British super-middleweight title in September.
The 34-year-old jumped up a division for that victory and admitted he probably waited too long to listen to his body.
“I am a different animal,” Williamson said.
“I feel better in sessions and it’s my natural weight. I can train properly and have proper session. I’m sleeping better and recovering better.”
Darlington fighter Williamson insisted he will “thrive” in the hostile atmosphere that awaits him in Leeds, with Simpson expected to bring a large following across Yorkshire from Barnsley.
Simpson has built a strong a loyal following since turning professional in 2019 and regularly meets fans before fights to hand over tickets in person.
“I’ve got amazing support, it’s everything a boxing coming up would want,” Simpson said.
“You see people like Ricky Hatton, rest in peace, and Josh Warrington did it and I’m building that base.
“It’s spreading across the country with people coming to get tickets from me.”
