NOTE: I strongly recommend that you order part number 6880309C92 from Motorola (1-800-422-4210). This is the service manual for the RLN4008B and contains the schematics and parts list for the RIB as well as some cable pinouts. You can use the schematic and parts list below until your service manual arrives.
Be aware that on the RIB schematic, you may not be familiar with some of the notation used for the resistors. You will find that 2k2 ohms refers to 2.2 kohms. This is done to prevent confusion between toner dots and decimals.
If you want to make your own PC Board, you can use this layout along with this placement diagram. Make the board 75 x 103mm and you should be fine.
A modification you may be interested in for the RIB. There have been reports of problems using the RIB on different computers. It looks like one of the problems might be a lack of negative voltage swing on the Busy out and RX (data out) lines back to the computer. You might want to try and change the value of R14 to 1.5k and R11 to 1K.
If you just need to program some of the Radius series of radios like the GP300, GM300, GP350, Maxtrac, Radius Mobile, etc. that only use Ground and Bus+, you can probably get away with building the programming adapter described here.
You could also try using some of the following:
There are no guarantees that these will work (they should), your mileage may vary.
Normally we don't get involved in assisting in the programming of radios other than Motorola's. This time we'll make an exception. This is a schematic of how to make the Motorola RIB usable for programming Vertex Radios.