Made one up today, worked perfect on a loose valvecover.
Will give a better report of use on a 74 750 tommorow, looks like tank has to be moved.
Tool consist of a drill bushing that fit in the tach drive hole , then using it as a guide you drill a 1/16 in or so hole into the seal.. at the middle point of it.
Then you insert a screw, grab that with vise-grips, then tap it out.
To re-intall seal, the tool/bushing, is used to push it back in..
works quite well by the look of it, will try to get pics taken, and a price for them in the next few days.