Revised 11/14/2016 : Adjusted pin slots on one side of plug to be more accurate to pin dimensions.
Atari SOI plug for making your own SIO cables for disk drives, SIO2Arduino etc. I have printed this and it works well. If you have suggestions please let me know in comments. I printed plug part with a .2mm nozzle with .25 parameters at .11 layer height it came out well, but your results may vary with a larger nozzle. It needs contacts to make it complete. I have tested it with contacts pulled from an old AT power supply's motherboard power connector, but the contacts can be purchased at: http://www.digikey.com/product-detail/en/molex-llc/0008500105/WM2300CT-ND/467825 (for example) these are reel, they also come in bags.
I have used this in a 400, 800 and 600XL and it is working great.
I used a .2mm nozzle @ .11mm LH for plug part.
All testing was with ABS. If you use PLA or other material please let me know how it worked.
The recessed holes on the case have built-in support that will have to be removed with a drill bit after printing.
Your print may require light trimming of any printer artifacts prior to assembly. A M3X12 screw & nut was used to attach the case halves. Use a small zip tie around the wire in the space provided prior to the wire exit of the shell for anti-pullout.