Japan didn't have any "ex motors". They have the sir 2 b16 and the d15b. Which do you have? Anyways, for a d-series, the best cam would be the crower stage 3, but you will need to do valve train, etc. A good cam that you dont need to do all of that stuff, the crower stage 1's or ZEX "stage 1" cam (they dont technically go in stages, but its the lowest cam).
If you have a b16, then you have way more options. From mild upgrade, like the ctr cams, to type d ericks racing Toda cams. Look into jun, toda, skunk2, crower, ctr, just to name a few.