It will bolt on.
When you go to buy the box, compare it to your ca20 box. There are 3 types of CA fwd boxes.
The ca16/18 ones look like the early ca20 ones, and are all cable operated.
The late model ca20 ones are hydraulic and the jap import ca18de fwd boxes were the same.
The easiest way to tell the differences is by looking at where the shifter bolts on, and the ca16 box is much smaller.
The ca18 import is your best bet, the ca16 one will blow quickly