RISE OF EROS - Chapter 4:

She was originally the young miss of the Marquis Estate, but became a peasant girl due to a mixed-up at birth.

Reborn in 2004, facing the age where pigs can be blown up, Lin Xuan, carrying the “Strongest Cottage King System”, started galloping…

- Description from novelbuddy

A scientific genius named Thomas Harrier was transmigrated to an imperial prince body after a car accident that took his life. He found out that he is in a world similar to our own with a timeline akin to early twentieth century. The body that he is occupying was the imperial prince of a failing empire who suddenly rose to power after a successful assassination attempt of his father. Unaware that the attack is just the beginning of what is to come. He faces many challenges throughout. Will Thomas Harrier be able to live his second life in peace while running an empire and getting it back to its former glory? Or will he succumb into a conspiracy lurking within the country's borders?

Expect some:

Cold war era techs.

Super battleship with advanced electronics, propulsion, and fire control systems?
Helicopters?
Missiles?
Modern medicines and equipment?
AC-130?
A nuke?
Challenger or Abrams or Leopard?
F-4 Phantom or MIG-21?
Colored TV's.

Everything!!!

PS. Cover not mine, I just found it on google.

In her previous life, she was a highly respected Heavenly Empress, but on the eve of her wedding, she was betrayed and died by self-immolation!