I went through this challenge when changing out my studs and decided to go with ARP Part #100-7708 (GM Camaro, Firebird, Vette). I searched through all the catalogs from Dorman, etc. with no avail. These are 2.5" in length and have a .509 knurl so they pulled in just fine without the need for reaming. But, they are m12x1.5 thread. The good news is that this is a very common metric thread size and standard as well as chrome nuts are available anywhere. The bad news is your stock TR6 nuts won't fit but I figure you didn't care about that anyway since you were considering 1/2".
I found a Dremel cut-off disc worked best for trimming to length.
Dave