I've done that exact thing! I used a Klein spindle and two #6003 bearings. No threading, no filing, no worries. Klein spindles are designed to be pressed into that size bearing without sleeves or snaprings.

Of course, I did this 15+ years ago--you may not have the same luck finding a spindle these days. I also did it for some customers who broke their Viscount spindles at the stupid snap ring groove.

You'll find the Viscount makes an excellent FG winter bike. And good for you going for a modern crank--the Viscount 17-bolt double doesn't take reverse torque well (DAMHIK).

Good luck!

Mel