jib sheet fairlead

I bought an x class sailboat some time ago to fix up. I'm still working on gel-coat repair. But for right now I need to figure out where to to put the jib sheet fairleads as my boat had a different set up that I cannot use. I'm not sure who the make of the boat is but i do know it is out of the 70s. It used to have some kind of copper rod on the hull infront of the mast step, the copper rotted away and I fiberglased the holes shut. How do I find out where to put the fairleads on either side of the hull.

 

The rod must have been a jib traveller. Locate the original holes you filled in. The extreme ends of the traveller, port and starboard, tell you where the sheet was led to originally. Stretch the jib sheet across where the rod used to be (as close to the original "rod" (traveller) height as you can remember) and it will fall on a point diagonally aft of the traveller, which is where the fairleads (or blocks if you want to avoid friction) should be located.

 

Could it be a self tacking jib system? If you are a strict singlehander that could have been of help, if not go for something more traditional.
More common are tracks running longitudinally to accommodate for different size of jibs and genoas and different points of sailing.

The deck should usually have some reinforcement in the area where a jib track would go to, or in the case of a cored deck the mounting area will either not be cored or have a higher density core to withstand the compression forces of the bolts.