Old cop,
I like what you said here but wonder, is there a current source for the old FBI load you mention? < snip>
I believe the Remington +P 158g LSWHP load is supposed to be close to what the FBI load was. Rem currently calls it "HTP" ammo, and unlike much of the fancy defensive ammo it's available in boxes of 50.
In my experience with my guns, the Buffalo Bore 158g standard pressure load with the same bullet makes exactly the same velocity as the Remington. (It also gives about the same recoil - BB may be wizards when it comes to pressures, but they can't fix that physics thing about mass and velocity and equal and opposite.) So the BB load would be an alternative for those worried about +P pressures in older guns.