To START align 0 deg marks on crank and cam gear, THEN you need to find TDC. The video link I have shows how to use a piston stop, there are others, this one is for determining if balance mark is correct. You are using a degree wheel, install degree wheel with a wire pointer that can be bent . Use the piston stop, find TDC. Adjust wheel to TDC, then degree cam. There are lots of videos on this, most have heads off.Let's try this from a different angle. A piston stop will get me in the neighborhood and then I should remove it and put my crankshaft timing mark at 12 o'clock. Since I am doing a cam change only on a good running engine I should be able the trust that the crank is right. So if the dot on the camshaft pulley is directly above the O on my Cloyes true roller timing set I can set my degree wheel to zero and degree the cam. Does this sound right?
Again video link is to show how to use a piston stop.