Do you need Color ? Do you have a scope ?

This chip---> 74ACT715
is available from digikey.

It will get you the basic Composite sync timing. It will tell you when to assert the sync_tip voltage and the black level voltage. I'm not sure if it tells when to gate the colorburst.

A 4051 would be a good start for switching between sync,black, and video.

Of course, you will need that 8051 to program in the default registers unless you manage to find the -R masked version.