Only two parts are needed. A Ronstan RF56510 block and one bolt with nylock nut.
I drilled out the horizontal pin above the spring of the original block. Then bolted the new block in its place. Done!
The ratchet block also has a becket so if more power is needed the original fiddle block can be put in place of the block on the boom in the same manner making the 3:1 a 4:1?
Full disclosure, I haven't sailed with this setup yet and won't be able to until spring.
Enjoy!