Yes.......and no.
If you are building more than one it sure is nice.
It is nice to be able to fixture up and measure a few things and know what shims to put in it to start with.
You can assemble and measure what you got.....disassemble......shim.....assemble.......m easure.....disassemble........shim......assemble.
A real pain, but if you only have one to do......
Then adjusting the shifter forks you can do with a make shift jig. Cut the side out of an old trans case.