I just received and installed 16 chips and they work in my 2000HD 
they are fitted into the A2091 board. the previous ones i removed were a mix of 80ns and 70ns (still working)
but if you need a source for 16 dram chips for this specific board, this is what i purchased (60ns chips):
MB81C4256A-60P 16 IC,DRAM,FAST PAGE,256KX4,CMOS,DIP,20PIN,PLASTIC
i sourced them from https://www.questcomp.com/
US company. Thanks for the recommendation. Will have to see how they fare with Mouser.
