I had a 6l90 the beefier version of 6l80 i my 79 c10 i drove it really hard it shift so fast it was really nice transmission it worked fine with 450rwhp.

In the corvette world they seem to handle from 550 to 600 whp anything fine but there was vette's here and there that had problems in that range to.

They don't have any upgrades that solves the issues that people have with them yet.