All the threads I've used on this engine are metric, mainly 1.6mm. The big end screws are 1.6mm high tensile with the heads turned down a little. I got them from RS Components here in the UK. They're a bit pricey but for something as important as the big ends I thought it was worth it. Here are the rest of the rods.
I'm just turned the taper on the crank and the dimensions on the plan don't work out - that is to say a 7degree inclusive angle don't produce a taper 0.5 inches long, which is necessary to accomodate a standard prop (at least). Did you come across this, how did you deal with it?