How to adjust timing if you can't see the timing marks?

I had Similar problem with a 360 in my 69 cuda and bottom radiator hose on the driver side. I bought a 1967 and back bolt on timing marker for the passenger side here on the forum. Think I paid 20$ shipped. Looks original. Before about 1968 the were not cast into the timing chain cover. I lined up TDC on the original right side I could barley see and made a slot with a Dremel tool on the pass side. Worked out great.