The A4ld has a removable bellhousing and it is simiply a C3 with a OD added, so the C3 should have a removable bellhousing as well. I don't know why you would want to though, because all C3s and A4lds are fairly weak.
There does exist a bellhousing to put a C4 behind a 2.3, however it is fairly rare. It only came in certain models of pintos during the 70's. I see the bellhousings come and go on ebay.