Bubba 95SN

The square 3/8" hole is what shape now? Find a can of CRC Freezeoff, it has a refrigerant to shrink offending part and lubricant so can be removed. Use as directed, amazing stuff, like a tv commercial. Try catch edge of plug with punch or chisel. If has some shape take 1/2' entension and grind to fir in bench grinder. There are 10-12 square drive tools. Renault had a 10mm square oil plug. (yea I worked at a dealership) I broke a 7/16" bellhousing bolt off. Used this CRC Freezeoff as directed started to turn with vice grips about 1/4 turn then removed with my fingers!