The first time I ran across TTY bolts was on a Ford Escort back in the 80's. I was warned by mechanics I knew not to reuse the bolts. I thought it was BS, but I bought new bolts from Ford on their recommendation. I was surprised that they were fairly cheap even at the dealer.
They had to be torqued to a some spec that I can't remember and then turned and additional 90* in two 45* increments. That second 45* really ramped up the pucker factor! I could feel the bolts stretching and it felt like they would strip out or break at any second. After that, I realized why they wouldn't survive another use.
I'll be replacing all the head bolts and the main cap bolts for sure. Actually, I think the short outside head bolts are reusable. The LS2 front cover and the new valley cover came from GM with new bolts.
Thanks for the comments on the LS Jerry. I'm an LS newb for sure. I'm learning that they have a few peculiarities from the old school engines I'm used to.