Knocking noise under load/acceleration

Hey guys, I have a rebuilt 350 bored 30 over that has barely 2000 miles on it. The first time I got to romp on it after breaking period I noticed a knocking noise. At first I thought it's my timing so I went ahead and got it timed to factory specs for 1970 Monte Carlo (that's what the engine builder told me to set it at). Still making the noise, my distributor went out. So I went ahead and replaced it with the msd HEI and set the timing again, still making the sound. I can't hear it in neutral, only under load and anything past 2300-2500 rpm. I've also recently replaced my carb with Holley 650 cfm and still makes that noise. At this point I'm starting to think that my exhaust is causing it(long tube hooker headers and a pair of glass packs right after, so it stops in the middle of the car). So I'm hoping you guys are kind enough to help me out here, and this car is my daily driver and only vehicle haha.https://youtu.be/Cc0ZM4tzUyY

Engine noises can be pretty simple, there are actual knocks that sound like two pieces of wood being banged together, there are ticking sounds, etc. and they are all different and all lead to a certain problem. Without more info, an actual "knock" under acceleration sounds like a rod bearing to me. Do you have a stethoscope to listen to areas, if not use a long handled screwdriver placing in on areas while holding it to your ear. You can find the area and then determine whats in that area. Hopefullly it isn't a rod problem.