Dandelion seed heads... Photo made with Nikon N90s, 55 MM Nikor Macro, PB4 Bellows and Ektachrome 100 at 6 to 1. This same bellows also fits the D1.

As all Nikor lenses and adapters are made to fit all Nikon SLR bodies, I doubt the PB6 uses a different mount. The trick to remember is that any body that integrates a verticle grip will require that you rotate the bellows to what would be their verticle position before attaching them. Once mounted to the body, they can be rotated freely without any hassle.

BTW... After tested the F100 and comparing it to the N90s, I purchased a new N90s. The difference in price will cover more than half the cost of a bellows or micro-nikor, and the performance difference could not justify the price difference. Of course I rarely use all the bells and whistles as most of my shooting is done in manual mode.