Late reply here.
But ive been running 87 in a 5.3 with a S475 turbo (5 PSI) in my daily.
You wont make much power with the setup at all on 87. I had to pull a lot of timing out and it just makes cool whistle noises now.
Its really not worth it. but if you do your own tuning you can get by with it on a daily just dont get in boost unless you have to.
I run COS5 (EFI LIVE 2002 Custom Operating System) so i use the "nitrous" timing retard for 87 octane to test it with. It feels like 100 rwhp loss on 87 with how its setup now.
Then you have to run majority of the fuel out to top off with 93 to be able to go back to the original tune.

 

Only casually mentioned for whatever the reason the EcoBoosts run well on 87 ( yes they run well... not optimized but still run very hard) is direct injection. Fuel can't preignite when it's not present in the cylinder. That's something you can never match with port injection so if you want to run boost on an LS run premium gas. If you can't afford the gas like all my idiot friends that buy premium only vehicles and then run regular... leave the truck alone. You won't be able to afford the engine after you grenade it if you can't afford the gas in it. Yeah premium is expensive in Canada... I live here too and use it in everything.

 

DI helps, but the biggest reason is the investment into head development. The chambers are designed to be able to produce very rapid flame front propagation, so you need less spark advance. There are two benefits from this...less negative work imparted on the crankshaft and far less susceptibility to spark-induced detonation. You lose less of the energy from the fuel working against the rotation of the crankshaft by igniting and generating pressure before TDC, You also delay the CA50 further into the power stroke which shortens the window of opportunity for detonation to actually take place. It can still detonate, but it will generate those pressure waves in a lower pressure environment which reduces the potential for harmful detonation.

 

I love lamp

and 91 and e30