Seems like in the back of the old Walker Exhaust catalogs, there were some ready-made size-adjuster short lengths of pipe? But I also suspect that FEW muffler shops ever stocked them as many muffler shop operatives seemed to take a bit of pride in making things themselves (even if they might not have been "the best"), by observation. Might need to snip the length of the existing pipes to get the right OEM-spec length, though.
Those supplied length/ends look very good.
Just some thoughts,
CBODY67