31/2'' header outlet...need to adapt to a 3'' header flange ideas

thanks for the repyls.... I know I can get them, just thinking I could buy a flanged 3'' header muffler and make a plate, to bolt it to my 31\2'' header flange.. I have only found one 31\2 header muffler.. not sure what way iam going with the exhaust.. looking for a low cost approach for now..
Sure, you could make a plate that would bolt your 3.5 header right onto a 3 inch pipe but it would be no good

A reducer will get the job done without causing turbulence and will allow the exhaust to flow properly