I recently scanned and just uploaded to archive.org Gregg Speed Building. It corresponds with the Anniversary manual which it refers to often by paragraph number, so you will want to have that handy as well. My understanding is that this was often the next text after one completed Gregg Speed Studies. It’s well worth a look if you don’t have a copy or haven’t seen it. Carlos, do you have any thoughts or tidbits you’d like to share about it?
https://archive.org/details/greggspeedbuilding/page/n4/mode/2up