1980s 318 questions

Drill, tap and plug the little holes under the exhaust ports. On the intake side of the head, if you mean the opening around the heat crossover, no biggie as they go nowhere.
Motor mounts - you need the brackets for your car. The truck brackets are different. Same for the oil pan. The truck pan will not work.
Torque convertor - might have an issue with the "button" that centers on the crank. 67 might be the earlier smaller button. And a later torque converter may have a different spline count.