21 hp to 25 hp swap

I replaced my 21 hp single cylinder for a 25 hp 2 cylinder Kohler.
My issue is that the muffler will not fit in the usual space. I is too far forward in the frame and does not allow the hood pivot bracket to be in place.
Has anyone else done this swap and have a solution for the muffler?

How would anyone know if they had done this swap as you have given no details as to what you swapped and into what? As far as muffler goes, time to cut and weld the pipes to fit muffler into correct space.