I am placing the info I have. You may or may not already be familiar with this:
398th Engineer Regiment
Mr. Joe Ciampa
(806) 233-5276
This is all I have at the moment, but I will continue looking.
Have you tried contacting NARA in Maryland? They have different records that St Louis does not, such as after-action reports and all the reports from S-1 through S-4. That includes daily, weekly and monthly reports from the units. It is worth checking out. This is where I received over 2000 pages on my dad's unit. I cannot promise you that you will find as much, but you never know what you will stumble upon. So if you want extensive history, please look there.
I have all the contact information listed in the Research section of this forum. Please let me know if you have any questions.
Best of luck to you,
M
Thank You Marion I had come across that phone number you mentioned and also had been to the NARA site but did not find much there. I appreciate all your efforts. Since the phone number is from Texas and a toll call I am trying to locate an address on Joe Ciampa but not able to get anything wihout having to pay for access. 
I will not be detered however and hope someone here has some recollection of this unit and possible my dad.
Thanks again