I was a tanker in the Army. Prior to and just after Desert Storm, the Army's last remaining Sheridan battalion was considering replacing the light tank with the LAV-25 but the decision was made not to do it for political reasons; the Marines wanted a monopoly on being the nation's medium weight force.
I was also in charge of the 2006 "test drive" for interim armored vehicles at Fort Knox (which was the home of armor back then). We checked out a couple dozen vehicles that we could buy off the shelf until the Strykers could be put into production.
While they appear similar, it would be like trying to make a 2010 Ford F-250 out of a 1980 Ford F-150.