aLL YOU NEED dAN IS A ROD TO SUIT THE SIZE OF the hole you're drilling in the bushes.
At least getting both from same supplier gives em half a chance of fitting correctly and only one person to blame when it goes pear shaped init?
I wouldn't worry about threading it or getting a tapered end, as most penturners certainly those on these forums have their own collect drive and mandrel saver.
All you supply is rod of the right size init?