It'll depend very heavily on what is decided for a rev limit. I'm wondering if we could have a 7000 rpm rev limit, but if something goes wrong and we have to lose top gear, limit the rpm for hanging in gear to 6500 rpm. Of course, drivers never really listen when you tell them rev limits.
The serious flow of the L92 heads plus a 10.5 compression ratio would probably get us close enough.
I spotted an '05 C2500 Express Van with a 6.0/4L80 on Public Surplus, but the bidding rocketed up to $2600. Ugh. Truck prices in Oklahoma... Meanwhile there's an '00 K2500 Suburban with rust issues in Pennsylvania that the seller can't get rid of for $2500.