Updated 15.06.2009

First of all, remove reversing unit (or delta decoder) and the motor from the locomotive.  Make sure that the locomotive works perfect mechanically, like the gears, wheels and connecting rods.  Clean it well before installing the new parts.  Carefully oil the rotating parts - if required.

Decoder:
Installed at the same place as the original reversing unit. I used the mini 60902 decoder (Märklin part number 603462).  The decoder is installed in the holder 456200.
f0 = front and rear light, three in forward direction, the two rear lower in reverse
f4 = acceleration and braking delay off

Later the decoder was replaced by one from the SBB Ae 3/6 II 10.421, Märklin set 37512 (part number 102155 or 611573, I think).  That is a remotely adjustable decoder  with the same functions and the same size  as the mini 60902.  The reason for replacing was the maximum speed, which can be adjusted to a much lower speed than the potentiometers on the mini 60902 allows.  With the mini 60902 the maximum speed at the lowest possible adjustment was approx. 160 km/h.  Now, by adjusting the speed (CV5) to level 15 with the Central Station, the maximum speed changes between 79 and 83 km/h.  Perfect.

Motor:
Installation of the motor itself is quite simple. You have to reduce the size of the screw head on the lower screw for the motor cover.  This is to avoid conflict with the rear left wheel.  I used a small grinding machine to do this.

Lamps:
The front lamp is installed in an old bulb socket (part no. 475030) glued to the front of the locomotive chassis, with a bulb socket insert from the 60903 conversion set.

For the rear lamps I drilled holes in the lower lamps and installed a light guide from the BR80 (3304, part no. 200690) and made a bulb holder of some old plastic parts and a SIL socket, cut to only two poles.  It is just visible in the photos.
For the front lamp I use 28 Volt T1 bulbs with long wire ends, cut to suitable length. I think the 610080 (22 Volts) are too bright.  The rear lamp is a 610080, as the light guide reduces the light intensity.

BR24, in this case Primex 30031 DRG 24 069:

Except for the front bulb socket, this conversion can also be used on the BR24, as it has the same locomotive chassis.  I have done it myself on a Primex 30031, DRG 24 069.
In the 30031 I installed a small lamp and two light guides from older NoHABs for the rear light.  I used the motor from a 60903 set and the decoder and small parts from a 60760 conversion set.  The "non-official" f3 output is used for driver's cabin illumination.  A small 28 Volt T1 bulb with a 330 Ohm serial resistor works perfect.