No codes I'm guessing, other than the occasional oil light blinking? When the ticking goes away with an increase in engine speed, makes me think low oil pressure as oil pressure is relational to engine speed. If your oil light is blinking, I would not drive it until I find out what the problem is. It comes on when oil pressure drops to about 6 psi. I would do an oil pressure test at cold idle and 2000 rpm cold, and then the same at hot idle and hot 2000 rpm. Your numbers should be in the range of: 30 psi @ cold idle, 50 psi @ 2000 rpm cold. 10 psi @ hot idle and 40 psi @ 2000 rpm hot. These numbers are approximate. There are any number of reasons why an old engine would have low oil pressure such as worn valve seals, worn rings, bad lifters, worn out oil pump, worn bearings or sludge or some crap blocking the oil pickup tube ect, but a rebuilt engine should not have these problems. I am concerned that you had to replace your water pump after only 7,000 miles following a rebuild. Sometimes (I'm not saying this is your case) when folks do rebuilds, they cut corners such as reusing old components such as lifters, cam or other parts which is a complete no-no. Get some oil pressure numbers and we can go from there, but DO NOT keep driving it with the oil light blinking!