Replacing a drive pinion oil seal



I have a 1972 Ford Mustang with a 3.25 traction-loc differential, 9".
I need to replace my drive pinion oil seal on the differential because
it's leaking. The Ford book says to use Tool 4851-k to hold the flange
when removing the pinion nut. Where can I get this tool or is there
something else that can be used? Also, where can I get a replacement
pinion nut, because once removed it needs to be replaced?

Thanks.

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