rapping sound in engine

i have had the head reworked installed new lifters ,new cam and knock sensor timing chain is installed corrctly and tight, engine run very well no sputtering or missing. i am going to change the timing chain and install a new tensioner as a last attempt to eliminate the rapping sound coming from my 96 2.4 L dohc engine, is there a test i can do to check
each cylinder piston wrist pins with the engine running? where can i get a good rebuilt/remanufactured engine block from if i decide to replace the one in my car . they seem to be very scarse