Although the DC8 CFM conversion was quite popular, IIRC there was only ever one 707 converted. The prototype 707-700 was the only one flown and it was not continued because it would compete with the 757 according to the official statement. However, I gather that the real reason may have been that there would have been considerable certification concerns with the directional stability not being compatiable with the power of the engines.
Of course many 707 airframes flew with the CFM in the guise of the C135 series of military aircraft, the French Air Force KC135s were effectively the CFM56 proving model. A friend of mine was part of the introduction of the CFM onto the USAF KC135 fleet and he aluded to the fact it was a real handful. It wasn't the crosswind which was the problem. I don't think it changed with the re-engine modification. It was the Vmcg and Vmca that caused the issues.