I think the problem is that maybe your BB axle its too short... why get new cranks if the problem is the BB??? The bb is italian or english? What frame do u have?
I been reading and apparently that set of cracks uses a 109 bb not a 107... no wonder u have clearence problems.
This is the set of cranks, right?
"Dimension/Bulletproof single-speed crank arms $40.00, 110 bcd, 165mm or 170mm length, silver or black alloy, 3/32" chainrings only, 38-tooth to 48-tooth available, use 109mm BB, Taiwan."
Hmm who doing 109's now? Will be hard to find. a 110 will work too... Hmm... maybe in this case it is posible to mix jis with iso... well.. resuming.. get a longer BB it will easier to find that the cranks u want, besides... do u have money to cast them??