Re: Skyhawk frame build / thoughts
Yowza, that's pretty crusty. You need a splined frewheel removal tool to thread that off of the hub, it loosens counterclockwise. IF you get that off of there, you can thread on a BMX freewheel. Some freewheels can be disassembled and reassembled, looks like this one isn't serviceable if those are two rivets I see in the smallest ring. Also, if it's that rusty, what do the bearings and races look like in that hub?
If you'd rather use the coaster, as long as your axle is long enough to have 135mm of axle between the locknuts and still get threads on the outer locknuts, you're good to add spacers which can be anything from a stack of washers to custom billet 12.5mm purpose made spacers. Might also be easier and cheaper than messing with that freewheel. That part ain't rocket science, you just thread off the locknuts, add spacers to each side and then tighten them back down carefully so as not to bind the bearings.