360 timing issue, retards before advancing?

Gotta think a little beyond the distributor here if all checks out with the bushings & advance mechanism. Make certain the drive gear is fully engaged with the cam gear & there is no excessive play (Lash) between the gears. Also look at the end of the distributor shaft where it fits into the slotted part of the drive gear as well as the slot itself for wear.
Be certain the pump drive part of the shaft is full engaged in the oil pump or it will try to climb the cam gear as it is revved & eventually break the distributor shaft. I've seen it happen.
Verify that you don't have any excess slop in the timing chain or gears. Remember that even "New Parts" are new in name only & can still be defective.
Good luck & keep us posted.