i took yall's suggestion of using a bottom bracket cup and welding it all together. it seems to have worked. course, we will have to wait for the streetfighter to be finished before i can test it. but it looks good.

for the disc brake mounts, i used a compass to draw the circles on a plate. i drew 3- outside, axle diameter, and where the bolts needed to be. then, after i cut them down, i drilled out the center, used a dremel to grind it (using my circle to keep it centered). then i marked 6 evenly spaces places on the "bolt" line. which is easy to do with a compass. the radius of any circle is perfect to "walk" the compass around the circumference 6 times. leaving 6 perfectly spaced marks. i drilled on those marks.

then, assembly. i used a 5/8ths bolt to clamp my BB cup, an axleshaft collar, and the disc flange together. in the picture you see a second shaft collar, that was to center the BB cup. turns out it was a perfect fit inside the cup.

drilling and tapping was easy. i swear, sharp drill bits are the best thing ever.

heres pics. enjoy!