My gear is a ESP Eclipse I CTM and I wanna replace the EMG 81 85 with a Dimarzio passive.
I know that I need to change the pots also with 500k, but which length should i take?
Long shaft or short shaft? I only know that long shaft are for Les Paul and short shaft are for Fender...
And also any capacitor suggest? Is it good to go for a Orange Drop?
The short shaft pots will work fine. The most common capacitor values for humbuckers are .022uf or .047uf. The .047 will roll off more mid levels along with the top end. They're relatively inexpensive, buy a few different values and try them out to see which you like best.
You also need to replace the stereo input jack with a mono one and you might need to add a bridge ground wire bc active pups don't require them.