What time does a stock 74 260z run the 1/4 mile in?

I have made the following minor changes how much of a time difference could I expect?

*change flattop SU's to early bell type

*280zx dizzy

*headers

*2.5 inch pipe with hot dog and resonator

Stock for 2 seater is about:

10.3 - 0-100

17.8 - 400m

don't know about the 2+2 but I would imagine a little slower