What do you weigh? You may be surprised how strong these wheels are... they can prolly handle a 90-100kg rider if built properly. Maybe throw a 2-4mm spacer under the left locknut to take some dish out (and just jam it in the frame) if you're heavier... the 25mm tyres should be appropriate for guys up to about 90kg, too.

As for the odd spacing of the Suntour freewheel, it shouldn't be too hard to replicate it on a Shimano freehub by messing around with spacers.