Yes, they'll fit just fine. You should have about 3/8" clearance from the inner of the front wheel to the strut body. 18" wheels will clear the SS 1LE brakes so no worries with the 19". WookWook has an
LT with an Apex squared stance in the size you're asking about - 19x9.5 +22 w/ 275/40r19. I run a similar setup in 18x9.5 +22 w/ 265/45r18 at all four corners on my LS with the 1LE suspension and upgraded brakes. It's definitely a flush fit that looks nice and aggressive. The 275/40r19 is actually a couple millimeters larger in diameter than the stock 20" size so they'll fill the fender gap virtually the same. You can use
willtheyfit.com to compare various wheel tire combos to the stock setup.
I ran the stock all-season tires my first two years with the car. They're fine for daily driving, but if you go that route for your tires they'll immediately become the weak link in your setup. Maybe consider a set of cheap snow tires for the 20s
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Modifications: 1LE (FE3) Suspension, Chevy Performance 4-Piston Brembo Kit, Kansei Corsa wheels w/ Pirelli PZ4 265/45r18