Tough call. If you're usually comfy on the old Acid 70 (narrow and low volume...but a good board though) it seems the Kode 74 is the natural replacement wich does add a bit of width and volume. But on the other hand, the Kodes are really controllable and handle fast waves and high wind really well. So if it hasn't been for the info that you used to sail the small A70, I would have recommended the K80 for your size and 5.3+4.5 (just like your dealer).
So again, a tough call. If you can not try the boards out, you simply have to think hard for a while. If you have a long history of sailing small boards and liking it, go 74. But if the issues of the sinking i lulls are something that hurts your sailing it might be worth it to a tad of the control a small volume boards gives you in high wind for some more light wind comfort. As far as 80 liter boards go, the Kode 80 will for sure be one of the more controllable ones.