The US Army were worried that the M26 would not be the right tank for all situations due to its weight and wanted a lighter tank with the same firepower, so they experimented with putting the Pershing turret on the Sherman, they did after all have a few knocking about

. This seemed to have worked quite well but the war was all but over, spending was being slashed and it was felt that it would slow down M26 production so it got dropped.
Im really happy with how it turned out, Im thinking of doing an M50 type of thing now with a 75/L70.