If there is a Harbor Freight Tools store near you, a rotary tool is an excellent investment plus, it's on sale, use a 20% off coupon and the price becomes $ 11.98.
Professional 4 Speed Rotary Tool Kit
All of my builds now come with a centrifugal clutch as standard.
The first few centrifugal clutches I installed, I machined the keyway for the Woodruff key and it worked well, but was extra work.
The last few builds, I have installed the clutch 'as is' with no problems.
With new engines coming from BGF,the three clutch posts are already shortened to use with the centrifugal clutch.