Harry Potter: Eclipse. - Chapter 69:

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.

I didn’t know this was a world inside a game. And I didn’t know my master was a mid-boss. “No way… wasn’t she supposed to self-destruct because of her personality?!” …I’m sorry.

[The 3000th issue of mysterious arrival is about to open! 】

【This is your only chance to redeem yourself! 】

In the global crisis, Wang Teng opens up his unique talent!

SSS-level talent – unequal exchange!

We are not zero yuan purchase!

But we are not equal exchange!

【The exchange is successful! You exchange half a box of instant noodles for endless extraction of SSS-level talents! 】

【The exchange is successful! You exchange a bottle of Sad Crisp Breeze for Douzhuanxingxiao! 】

…

Since then, Wang Teng has opened a new mode of exchange.

- Description from novelbuddy

Wen Zhixing has transmigrated into the world of cultivation and has been unexpectedly abducted to the Wondrous Palace, where is full of infamous female cultivators. However, with his Immortality System, Wen Zhixing discovers that he could see their “Fortune Fragments” and take advantage of these Fragments by consuming his lifespan.[ Acquire the constitution: Revival of the Withered Tree.][Revival of the Withered Tree: Blazing Gold Quality. Can rejuvenate a withered body. Each time the body enters a withered state, it will undergo nirvana. After nine nirvanas, it will shed its mortal form.]...