Naruto: Copy System - Chapter 600: [] : You’re Too Naive!

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 is the ruler of the mercenary realm, an overlord that gives headaches to the leaders of any country! For the sake of his friends, he’s willing to sacrifice himself; for the sake of his family, he does not hesitate to spill blood! He is a dragon, one that soars above even the highest of heavens. He’s a power that advances triumphantly through unstable situations, stirring up both the winds and the waters.

“Alas, this life is a failure; let’s see what the next life holds.” ... “The second life has ended, calculating results... Final rating: C+. Rewards based on rating: You may choose to inherit one item from Constitution, Skill, or Talent. Please select?” “Hmm, I choose to inherit the Talent ’Dynamic Vision’.” “Talent inherited... Congratulations on achieving the following lifetime achievements: Innate Grandmaster; Blessing of Many Offspring (10/10)” Achievement rewards: Two random rewards. You may draw from Constitution, Skill, or Talent, or choose to upgrade Talent level. Please select? ... A reborn individual, in possession of the treasure ’Hundred Lifetimes book’, reincarnates within the Cultivation World, undergoing endless cycles of rebirth without the bloodline ending or the soul perishing! The family he established ten thousand years ago has now grown into a massive entity that spans the heavens. The disciple taken in casually eight thousand years ago ultimately became the founder of a Great Sect in the Immortal Realm. The pet raised three thousand years ago has evolved into an unparalleled Demon Saint of the Otherworld. ... I am Zhao Sheng, and I shall cultivate life after life until Ascension!

Imagine being forced to live, after death, as incorporeal bodies trapped in a vast space of nothingness for thousands of years, with nothing to do but exchanging past memories with other cohabitants (read: weirdos). Everybody wanted out, but there was no way to leave the Void…

Until one day, a young man was finally summoned, as a powerful but reluctant mentor, by a bubbly and motivated but completely naive young girl. Baiyi, finally out of the Void, was the only one who could save all of the other 32 souls from their prison and his summoner might just be The Key to their freedom.

However, Baiyi had to use the techniques and abilities the other souls had taught him throughout the years, and together with his own extensive knowledge of anime and game tropes from his shady and dangerous past as an otaku, to face the biggest challenge of them all: training the clumsy young girl he was forced to partner up with… into a competent sorcerer!

This is a story of heroic adventures, cunning strategies and romantic tales. How will our MC thrive in a world completely strange to him? Where will his ambitions and abilities take him in the palace?

- Description from Novelupdates