It'll bolt up, probably - check though, because some of the PD motors and 20Vs have a different bolt pattern.
You may need a different way of getting a signal to the speedo, as some 6-speed boxes don't have a speedo drive.
You'll need the shift-tower and cables, as well as the mech on the gearbox. Some of the late shift towers are quite cute-looking, so you might like to sort out some way of bolting the complete assembly to the TOP of the centre tunnel - puts the shifter closer to hand, too.
Do be fair, you shouldn't really NEED 6 speeds on an ABF - it has quite a rev range, unlike TDIs etc, which really DO need 6 ratios to help them out.