Any old Windsor block will drop right in. But as it's a four-cylinder, why not be amusing and put the SHO turbo 2.3 in it?
Note that a 2.3 turbo will bolt to a C4 with the appropriate bellhousing. (1974-76 Pinto/Mustang II)
Former Panther:1982 Marquis station wagon.
Current Panther: white 2011 P7B, former Carroll County NH Sherriff car...heated mirrors, power seat, power pedals, cruise, CD player.