Shake rattle and roll

Got it. If this isnt the entire issue its a huge part of it that needs to be fixed immediately. Made it a point to study the fuel pressure today. First start up when cold im getting 7 psi. After idling for 5 minutes it drops to 6.5.. then 6. If i give it light throttle i watch it sink down to 3 psi and start fluctuating. As soon as it hits 3 the motor throttles down and what I thought was lifters (must be dry cylinders) start clacking like hell. Ive already replaced the fuel pump with the old(er) pump I had on the old motor and fuel filter. Plus all the fuel lines in the front. Im going to drop the tank and replace the original hoses in the rear to make sure they arent sucking air and check to see gunk is glogging up the pick up in tank. Anything else im missing? Any way a carb can cause low fuel pressure?

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