Immortality begins with Becoming an Alchemy Grandmaster - Chapter 58 - Broken Sword Ten-year Old Fan, Self-invited

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.

Tian Man Continent is a world of martial arts. A young boy named “Su Yi” led countless yao (monsters or demons) and overrode countless families who had thousands of years of history. He rose abruptly in the world as the brightest star in the sky. He married beauties and walked towards the peak of of the world, and finally ascended onto the thrones of the ancient gods!

- Description from novelupdates

Mythical Abode Mountain, Cloud’s End Cliff, the most dangerous of Azure Cloud Continent’s four deadly areas. Cloud’s End Cliff’s base is known as the Grim Reaper’s Cemetery.

Seojin transmigrated into the novel named ‘777: The Crowned Sovereign’ as Seven, a side character.Here, he was the seventh child of the seventh archduke of the seventh kingdom of the seventh continent.On Earth, he was raised by his seventh stepfather and the child of the seventh ex-wife of the seventh mayor. He even had his seventh maid quit the job.He was also the seventh reader of the novel he transmigrated into.[Welcome, Seventh Reader! Your loyalty has been awarded.]With this many sevens, will he curse it as an unlucky number or… praise it seventy seven times?…Note: The author is a complete newbie and this is the seventh draft. Please don't expect this as such a grand story.Thanks. Merci. Danke. Bedankt. Terima kasih. Gracias. Salamat.Congrats! You just learned how to say ‘thanks’ in seven languages! ;P