Sneaking in without a roll cage

With a battery in the trunk, and no shut off, you won't (or, at least at my track) get past tech. Any new car that tech hasn't seen gets the belts and helmet looked at, and the shut off checked, at a minimum.
However, if you DO get past tech, run a 1/4 mile track, and shut it down at 1000 feet. Don't make it obvious and get on the brakes and run 59 mph. There are lots of conversions from 1/8 to 1/4.
If you only have an 1/8 track, run hard to 330, and back off a bit. 330 can give an accurate assessment for 1/8 and 1/4 too.
If you flagrantly throw "too fast!" in their face, they WILL bounce you. One of the local tuner shops brought out a standard cab Silverado 4x4 to run at our track. Turns out it had a twin turbo 427 LS. (How it got past tech in the first place is a mystery) .No cage. No bar. No belts, other than stock 3 point.

Ran 5.70 something, 125mph eighth.
They got bounced before they got a timeslip, before they got off the return road, told don't EVER bring that thing back without every piece of safety equipment in the catalog.