I have a knock I can't get rid of. However it is not always present. If I drive the reasonable, no knock. Seems it appears after revving the engine and then at low to mid rpm's. The engine can be cold or hot.
I have shimmed the rods more times then I care to. The mains were setup correctly when rebuilt. Does not sound like piston slap.

Check the endplay of the cam.

Tyrone,
If you can get the knock while running the engine with the car parked, open up the hood with the enigne runing and the knock occuring, ground out each cylinder one at a time with a screw driver by shorting out the spark plug to the head. If you can get the knock to stop while shorting out a particular cylinder, you will have established the problem as either that connecting rod or the main bearing adjacent to the cylinder. If it is the center main, you may get the same results grounding out cylinder #2 or #3.

A worn timing gear will sound just like a rod knock. If you have a generator, you can try to rock the generator gear from the oil filler opening and see if you can get the knock (while the engine is NOT running). If it is your timing gear it will require replacing both the large and small timing gear. The large one on the cam shaft can be changed while the engine is in the car, but the smaller one on the crank, although it can be replaced while the engine is in the car, is better done with the engine out.

A less likely knock is from a loose fiting fan pulley on the crankshaft. A loose pulley will make a lot of racket but not really a rod knock sound. There are many threads on how to fix that one.

I had a knock 11 years ago, in my 27 Tudor, that was heavy like mains. Turned out to be looseness in the trans. Can't remember exactly where, but it had to do with a keyway. A couple veteran T techs before me tried in vain to eliminate thie noise. It was the only T trans I ever had apart.

Noise from excess clearance with aluminum pistons can sound much like a rod knock...