The Art of Wealth: I Became a Billionaire - Chapter 42: Elliot’s Rescue

He died on the wedding of the girl he had a crush on, after a long and successful career. After convincing Yama to send him back to the world, he decides to fix the areas in which his life went wrong. Realizing the lack of love and romance in his past life, he sets out to conquer the hearts of various women.

- 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.

He hadn’t even met his so-called “fiancé” when he found himself labeled as an “abandoned husband.” Discussing marriage had always been a sensitive topic for him, but he ended up falling victim to a cunning plot that involved marriage, dowry theft, and a seemingly arrogant “high and mighty” family. Those individuals who posed as “orphans” and “villains” wore sinister grins on their faces. They audaciously conspired against this young master, ensuring that peace eluded his family day in and day out. And now, what was this? The supposed “orphan” had suddenly transformed into a royal grandson?! Tears welled up in Lin Yuxing’s eyes as he exclaimed, “My love, let’s continue our days of togetherness!”

Chen An traveled to the world of cultivating immortals, and his cultivation talent was extremely poor. He was stuck in the third level of Qi refining for many years and could not make further progress.

Seeing that there is no hope of cultivating immortality, he chooses to return to ordinary life, and marries a wife to enjoy the ordinary happiness.

As a result, on the night of their marriage, they returned to the fairyland overnight.

It turned out that marrying a wife and enjoying ordinary pleasures was his way to become a fairy, and it could directly save him thousands of years of detours.

- Description from novelbuddy