My 68 castig 318 timing cover cracked trying to take front main seal off. The timing is on the left. Can I use a cover off a 318 outback where the timing is in the right?

The water pump outlet is on the drivers side. If you use the newer timing cover, the pump outlet will cover the timing marks. You could use the long snout water pump that has the outlet on the passengers side but that would mess up the pulley alignment and radiator hookup.

Yes, Find exact TDC with the piston stop in the #1 plug hole & make a new paint strip with white paint on the dampener lined up at the zero mark on the DR side timing tab. If you ain't got a dialback then in addition make several new marks clockwise on the dampener from the TDC slit & 0.0632683" is 1 degree & (4) marks in addition to the TDC slit works for me, 10-15-20-35.5 which 35.5 is 2&1/4" (2.246") works for me. Some dampeners have a partial slit line at 90 deg intervals so use the one that lines up which I think is the one 1/4 (90 deg) turn clockwise from the original TDC slit & paint it across & wouldn't hurt to check exact TDC there also. You have to aim the light PERFECTLY to see the marks with the pump nipple/timing tab on the same side but it is doable & if for example you remember that your marks are tdc/10/15/20/total (write em down as you will space em) then if the third mark is at zero on the timing cover then you know you're at 15BTDC