how to convert a beseler 8181 color head to fit on beseler 45mcrx

I acquired a Beseler 8181 color head that normally goes on a Beseler 23c enlarger. Howerver, I have a Beseler 45mcrx and would like suggestions on how to make the two fit . The 45 has a larger diameter diffuser than the one on the 8181. Thanks for any help.

If it's designed for 2x3, then it won't cover 4x5. So even if you could rig up some way to mount it, why bother? Get a 4x5 head for a 4x5 enlarger.

Thank you for response, figured as much. Will look for one, hopefully will find it. Lesie