I use double-hump heads on lots of engines, no hardened seats or exotic rebuilds. A good valve job and bolt 'em on. They run for years, then when the seats pound out, sell them to a rebuilder to put seats in them. They last as long as the rest of the GM hand grenade.
If they're just a bit worn, grinding 1.94/1.5 seats out to 2.02/1.60 valves gets another use out of them.
The one time I had seats installed, the inserts were rolling around in the back of the truck when I got home! Glad I didn't get that guy to assemble the heads, I'd have put them on before I realised he wasn't as good a machinist as everybody claimed.