One of the simplest ways I've seen it done was to take the two pieces of tubing, one in the front and one in the rear of the engine block.
Square them up, shoot a little paint in each engine mount hole onto the tubing. Let it dry for a bit, then take one of the mount bolts and insert it into the holes on the engine and twist it around to mark the fresh paint. Remove the engine, and you should have 2 tubes with 4 holes marked for drilling. Center punch the holes and drill straight down through the tubes. Drill press helps to keep the holes straight through.
The tubing only needs to be wide/long enough to span across the bottom of the engine plate, side to side, front and back.
Spray something like acetone on the fresh paint on the engine block andthe paint will come right off.