Yes the jack should fit under the truck. It raises and lowers with a half in chuck with an impact wrench. It should raise 3ft..... I'm not sure. It's only like $50 on sale at Harbor Freight.

Part's that old?!? ANY Autozone, Checker, NAPA, will have any replaceable engine/drivetrain parts. Have you even checked?!? The 300-6 and trans stuff is really easy to get parts for as was used for decades.