The Summoned Monster That Is Summoning Another Monster - Chapter 73

When Li Xianyu was 20 years old, he received his father’s inheritance, an 18-year-old great-grandmother who was incredibly beautiful.

Li Xianyu: “Great-Grandma, why are you so young?”

Great-Grandma: “That’s because I died when I was 18 years old.”

- Description from Novelupdates

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.

Yuan Fangguo, who was reborn and returned to his college days, had nothing.

Fortunately, he stood on the cusp of reform and opening up. Facing the waves of the South China Sea, Yuan Fangguo and his brothers and sisters opened their arms and greeted the wind and waves.

Challenge… He secretly vowed to set a goal. My small goal in life is not to make 100 million, but to let the people I want to help earn 100 million easily.

- Description from novelbuddy

A decade ago, the first dungeon gates appeared, but some vanished before they were ever conquered. The MC, a low-rank hunter, awakens the Lost Gate System, granting him access to these forgotten dungeons where legendary monsters and artifacts are trapped. Each completed lost gate grants him absurd power, but also reveals terrifying truths—these dungeons are prisons for ancient beings who want revenge.