Well that can be quite an experience.
Hopefully my explanation of how to proceed is helpful to you. Just building from plans can be difficult, you will find your first builds like this a bit challenging.
When you start designing you own and building, it gets even more entertaining.
Just keep in mind often with these older design they use sectional views and don't tell you that piece is actually larger, it is assumed you already know that like your question about the spreaders. It doesn't help that he used a center line and did not include the zig-zag break line on the spreaders. So watch for that on other portions...
Good luck with the build you should have a nice airplane when your done.
Here is how it should have been done...