Well somebody else brought up Bliar, but let's put him to rest.
There were no alternatives for re-engining. It was a long range, heavy fuselage, and its economics would never have worked out. I think its empty weight was several tonnes more (maybe up to 7) than a 707. At the time it mattered, no other engine could have fitted the bill- you couldn't get paired CFM56s on either side. A wonderful machine, but of its time- the 60s. That darn Bill Boeing got the right formula.