I can't give you the exact way but it does not seem like you can do it as such.

Beogram 4002 is '70s

Beogram 8002 is '80s

Beocord 9000 is '80s

Datalink which allows connections between systems did not come before the '80s and you would need a Beomaster or two to be able to connect the above 3 things to start with. 

Then it is a matter of the Beomaster being able to connect further via mcl/ml etc. and powerlink. 

I mean Beomaster 6000/8000 is out of the question though perfect for the 2 out the items you want to connect.

Using a Beomster 6500 could do well with the Beocord 9000 on aux or MCL2AV beolink but I do not think the 2 Beograms will work. In that case the Beogram 6500 goes to Beomaster 6500 and that will go to the converter instead of what you got now.

It would better to get a matching Beomaster 4000/4400/6000/8000 to the Beogram 4002/8002 but let it stand alone as an independed system if you are still keen on the idea you want.

Thank you!a switch-box:http://soundsheavenly.com/input/18-aux-input-switch-box-for-multiple-input-devices-to-one-aux-socket-4-way.html

You still need an RIAA amplifier for each of your turntables plus, if you want to record from the turntables to the tape deck, you will need record in and out connections from the amplifier for that. 

http://soundsheavenly.com/beogram-record-players/12-pre-amp-kit-for-bo-beogram-and-all-turntables.html

for recording on beokord use the output of the converter

http://soundsheavenly.com/input/17--ufo202-.html

Ok?