Here you are, right click, save as:
http://home.planet.nl/hille501/Speedster/ECU_frame.doc
http://home.planet.nl/hille501/Speedster/ECU_frame.dwg
http://home.planet.nl/hille501/Speedster/ECU_frame.dxf
3 files, one of them is a Word doc for those who have not the correct software to open the CAD drawings. The .doc drawing has all dimensions in them, the CAD drawings not, but they are to scale. The CAD drawings might be easy if you want to laser the plates.
If you plan on installing the 68mm TB later, you could consider to make the hole 67mm, the size of the opening of the manifold (check). This will allow you to switch TB's quickly. But I have to check the flange of the 58mm TB if that extra big hole will not give any problems.
I made my plate using a jig saw, no problem:

Good luck!