What have I done? Video attached: Bad sound after oil change on ol' Blue

[RichardJ]

>> at the base of the radiator, there was a piece of metal placed under it to support it (the frame piece is rusted out underneath) and this looked like it had gotten chewed up a little bit.<<
>>All I actually had to do was smack that metal slab with a hammer to tap it back out of reach of the fan. And the TINK was gone! <<

Did you do something during that oil change that would have caused that cross member to be moved into the path of the fan?

>>turned it around and gunned it up the hill in reverse to get it in position for the oil change .... I admittedly clutched it at high RPM and it did "kangaroo" on me pretty hard on the way up.<<

You need to check the motor mounts.