The 101 hook was only listed in the 1970 only factory parts book for use on Plymouth E-Bodies. According to a 70-71 factory parts book, dated Jan 72, it was replaced with the 100 A-Body hook.

I have a copy of an engineering print dated Sept 70, that still shows the 101 as the only hook for 70-71 Plymouth E-Bodies. It doesn't mention the 100 hook.