With the ballast that is correct. Once you remove the ballast, all you’ll have left is the mains. This will leave you the Hot and Neutral wires. Since the tombstone in the fixture is a shunted one, you can’t plug the mains into it as it will short out. So you replace a non shunted tombstone on the side where mains needs to make contact to the two active terminals, either on the left or right side, depending on how you position the T8 tube.
You are making this way too complicated. You could simply replace the existing bulbs with two LED bar lights that go for under $2 each from an overseas vendor (14-21 days delivery) and power them with a 24W universal driver for $5 https://www.ebay.com/itm/Universal-DC-12V-24W-60W-2A-5A-Switching-Power-Supply-Driver-for-LED-Strip/112734551939?hash=item1a3f80bf83:m:mkrAxSGdbsuetAX3GPhLGYw It will fit neatly where the existing ballast is located and the output for the two bar lights would be equal to using two T-8 lights at a fraction of the cost. The new T-8 bar lights that plug in the existing holder but don’t use the ballast are just strip lights with a driver enclosed in the tube. I see a set of four of them go for $39 on Amazon whereas one bar light is only $1.39 postpaid 50CM 12V 36 LED 5630 SMD Hard Strip Bar Light Aluminum Rigid White 50CM 12V 36 LED 5630 SMD Hard Strip Bar Light Aluminum Rigid White W1L2 for sale online | eBay Of course, if you can scavenge an old 12V 2A DC converter (look for one with an efficiency rating of IV or V on the label) it is even cheaper. I picked up many a converter from of the local second hand store for a buck or so. I’ve used them as undercounter lights, closet lights, and garage lights with good results.
Ok without reading any more of the confusion on an old topic I am an electrician in my state. No offense to anybody but there are way too many indians and not enough chiefs in this clan making things way too hard.
Did you ever figure this out since it’s an old topic?
Not for anything but ripping out the ballast and changing a tombstone from a shunted to a non shunted is the simplest retrofit. I’ve already had to do that at our shop. 16 T8 fixtures. It’s super easy.