Update:

I called ARP they don't make anything with more than 1/2" course threads unless they custom make it.

I did order a pack of the Trick Flow P/N earlier in the week (they have just a tad over 1/2" of threads) and have been mocking things up, but didn't feel there was enough thread in the heads, but on the way home from work today I got to thinking. On my Edelbrock heads anyways the threads for the rocker shafts don't start until .40" in the hole.

With the factory bolts there is .871" of bolt under the shaft resulting in .471" of thread engagement.

With the Trick Flow studs there is .918" of stud under the shaft resulting in .518" of thread engagement.

So the Trick Flow studs have .047" of more thread engagement. For some reason I was thinking that since the bolt had .871" of threads showing under the shaft I needed atleast that much on a stud, but in reality, not all the threads are being used.

The overall finish on the TF studs isn't as nice as I'd like, so I did order a set of ARP studs that are to be delivered tomorrow (should of taken AndyF advice and order both at same time). I'll mock them up and see how they compare to the TF studs.