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

Sure, I have made new TDC marks in the strangest places, like
Laying on my back under a truck, or
drilling a hole in the bellhousing and marking a tooth on the ring gear, etc.
Just make one any where you want it to be. And you don't need a tape either if you can do a lil math. Or if you have a dial-back lite.