Need some advice on slicks for my '67 Notch

I have never ran slicks before so I'm a newb in that area. Wanting to take my car to the track a couple of times this Summer with some other friends.

I have a spare set of rally rims now and thinking I would buy another pair of 15 x 8 for the rear, to be left setup with a set of slicks so I can just swap out all four rims & tires when I want to bring it to the track. I would be trailering the car there.

Couple of questions:

1. What's the biggest size I can fit on these 15 x 8 rims under my stock body 67 notch without any mods?
http://www.wheelvintiques.com/index.php/chrysler-rallye-61-series.html

2. Tubes or tubeless slicks?

3. Any guesses on what kind of ETs I might expect, 1/8th and 1/4 mile?

4. Considering a set of used slicks for this year, might only get out there once, maybe twice. Things I should beware of?

My setup:
340
10.5:1
J heads with 2.02 intake valves
508/292 comp cams
Holley 750 dp on M1 intake
727 reverse manual valve body with 4000 stall converter
4.56 gears
MSD with 3000/7000 two-step rev chips

I did a couple of searches but didn't have much concrete luck.
Any help is much-appreciated!

-Doug