Yes, great timing! Welcome aboard. I'm sure timkins will be very pleased to hear from you! 
I too have the volumes you speak of. In fact I have ALL three volumes and have gotten a lot of information and photos from them too.
The three-volume set was kindly given to me by my dear friend Al Kincer of the great 48th Combat Engineer Bn. I love the maps that are included too. Great detail. Even shows where they constructed baileys, cleaned up mined areas, etc.
Several years ago I contacted the US Army Engineer School Historian to see if there was still a 175th Engineer Rgt either active or Reserve or an organization or veterans group but only found that it had been deactivated at Camp Patrick Henry, VA (now the site of the Newport News, VA airport) in 1945 and that is that.
You say you contacted the school. Did you contact the Army Corps of Engineers Historian's Office? They have folders on virtually every WWII engineer unit. That is where I amassed a wealth of info on my dad's unit.
You can also obtain the de-classified docs from the National Archives. I hired a private researcher to gather ALL the documents on the 540th Combat Engineers from College Park, Maryland. I ONLY have 2/3's of the docs right now and they total approximately 1500 pages. I am using this info for the site and for the book I am writing on the VI Corps Engineers.
Let me know if you have any questions. Always happy to help out the family members of our engineers. 
Proud Daughter of Walter (Monday) Poniedzialek
540th Engineer Combat Regiment, 2833rd Bn, H&S Co, 4th Platoon
There's "No Bridge Too Far"