I managed to get 2nd's which are fine. It's only aluminium so you can probably get away with those or give them a quick tickle on the grinder to add a bit more taper.
Good luck.
I got the taps from a little tool place in the UK called Tracy tools a looooong time ago, but you can get them on ebay and from Amazon usually (at least in the UK). You want Left and Right hand version of 9/16" 20 tpi BSC (British Standard Cycle).
Cranks were from an online retailer (bike shop)...
Couldn't buy them unfortunately, had to make them from 175mm Creo ones
150mm crank making
160mm is the shortest you can buy off the shelf. There are quite a few frame builders etc who will shorten cranks for you, or you can buy the taps and do it yourself if you have a drill-press or a mill.