As you may already know, the IC-765 has IF-shift but no passband tuning. There is, however, a simple mod originally designed by Gerd Henjes, W2ISB, which allows the IF-shift button to tune the passband while the IF-shit button is in OFF position. This mod is described in the VE3HUR IC-765 notes and reproduced here with some illustrative pictures, as well as a video demonstrating the difference between PBT and IF-shift