Let's see if I have this right: The Top 3 from each of the 4 A Mains from Tuesday-Wednesday-Thursday-Friday all advance to Saturday's A Main. Positions 4-10 in each of the aforementioned weekday A Mains go to a B Main on Saturday Night.

https://www.chilibowl.com/news/?i=55890

You cannot tell the drivers without a scorecard, so with that format/formula, here are the drivers, as of the end of Tuesday Night, that are locked in for Saturday Night:

A Main:
01 Kyle Larson
63D Brad Sweet
7BC Tyler Courtney

B Main (one of):
4 Tom Harris
67 Logan Seavey
57BC Giovanni Scelzi
3N Jake Newman
05 Brad Loyet
118 Scott Evans
7K Justin Peck

Larson was already guaranteed a spot in the A main for Saturday since he won the race of champions last year, i think winning the race yesterday will improve his starting position

The only one guaranteed a spot as a provisional, is Christopher Bell. He was last year's Champion. Unless they decided to change something for this year

According to this interview that I posted the link for, Larson stated he was locked into the feature since he won the race of champions. Larson is actually driving a car that is owned by his dad but Keith Kunz prepared it and maintained it.
here’s the link: http://jeffgluck.com/chili-bowl-night-1-kyle-larson/

Updated after tonight (Wednesday night):

A Main:
01 Kyle Larson
97 Rico Abreu
63D Brad Sweet
91T Tyler Thomas
7BC Tyler Courtney
27K Kevin Thomas, Jr.

B Main (one of):
4 Tom Harris
1 Sammy Swindell
67 Logan Seavey
35TE Chris Windom
57BC Giovanni Scelzi
71 Ryan Robinson
3N Jake Newman
73X Jason McDougal
05 Brad Loyet
2R J.J. Yeley
118 Scott Evans
05T Gary Taylor
7K Justin Peck
2ND Jeb Sessions

Updated after Thursday night:

A Main:
01 Kyle Larson
97 Rico Abreu
71W Christopher Bell
63D Brad Sweet
91T Tyler Thomas
17W Shane Golobic
7BC Tyler Courtney
27K Kevin Thomas, Jr.
71R Chase Johnson

B Main (one of):
4 Tom Harris
1 Sammy Swindell
24 Tracy Hines
67 Logan Seavey
35TE Chris Windom
49ER Caleb Armstrong
57BC Giovanni Scelzi
71 Ryan Robinson
87 Ryan Bernal
3N Jake Newman
73X Jason McDougal
77P Billy Pauch, Jr.
05 Brad Loyet
2R J.J. Yeley
2D Matt Sherrell
118 Scott Evans
05T Gary Taylor
4J Tim Crawley
7K Justin Peck
2ND Jeb Sessions
5 Jerry Coons, Jr.

By T.J. Buffenbarger
TULSA, Ok. (January 9, 2018) — Kyle Larson dodged the adversity he has faced the past two years at the Chili Bowl Nationals during his preliminary night to win the main event during Warren Cat Qualifying Night Tuesday at the Tulsa Expo Raceway. The win was Larson’s Fourth career preliminary win and first since 2015.

While the victory was for Larson, avoiding misfortune that could keep him from being locked into Saturday’s finale was just as enjoyable.

“It’s cool to be back up here on the stage,” Said Larson. “This is probably the first time I’ve had a smooth prelim night in probably five or six years it feels like. It was a clean night and hopefully we can keep it going on Saturday,” said Larson. “Extremely excited to lock in. Last year I got to watch the 55-lap race, and that was no fun.”...

I think Jeff Gluck is mistaken. No mention of Kyle being locked in during Chili Bowl, at all

Wouldn't some of these guys go to a 2nd B? There's already 21 drivers listed, with tonight's prelim night still to go.

I think that's what he means by "one of"; probably can't figure out the split just yet...