Termination for 74LS279A unused set and reset input and CD54HC4538 usused 2Cx and 2RxCx inputs

2Cx and 2RxCx can float or they can be tied to gnd.

is it ok to tie the 74LS279A's both the Reset and Set input Low?    No it is not OK. That is an invalid state an anything could happen.

What do you mean  "anything could happen"?

Thanks,

Stephen

The output is unpredictable

Also, in my original post,I forgot to ask about CD74HC4538M's R_N reset input.  Should it be tied low?

Stephen 

By unpredictable, do you mean that it will go high or low at power-up and stay at that state.  Or do you mean that it will randomly switch states ever once in a while both at and after power-up.

The first one is not a problem since I am not using its output.  

The second one will cause it to use more power and should be avoided.

The part will more than likely consume more power. Using the part this way has caused problems in the past. 

If you tie the reset low then the output will never change. If you mean at power up where it is pulled by a resistor until the control signal is asserted then yest it is a good Idea. 

Ok.  I am going to connect the inputs as shown below (Just to make sure I understood you correctly).   Does it look correct.

Stephen

CD74HC4538M:
   Connect R_N Low
   Connect 2A High
   Connect 2B_N Low
   leave 2Cx and 2RxCx Open

74LS279A: 
   Connect both Inputs High