Wolf of the Blood Moon: A Blood Magic - Chapter 41Book 6:

Lingyun, a fierce and savage cultivation genius takes over a dead teenager’s body. Coincidentally, they are both named Lingyun. Set in a alternate version of the 21st century, teenager Lingyun has been killed by someone with a grudge.

【Brand New Setting】【Fully Developed System】When you awoke, you had become an official known as “Minister of Agriculture” in a fantasy game.“Dynasty's Prosperity” version: You diligently cultivated the “Seasonal Order,” from “Harmonizing Winds and Rains” to “Summoning the Winds and Commanding the Rains,” from “Bountiful Grain Harvests” to “All Things Flourish,” commanding the seasons and quietly developing.You achieved minor successes, joined the army on expeditions, and controlled the “Four Books of Agriculture.” You froze thousands of miles of great rivers to pave the way for the army. With “Miasma” you slew enemies, “Fog Shadow” obstructed tens of thousands of troops, establishing unparalleled military exploits and rising to the position of Director of Agriculture, secretly seizing the fate of the dynasty, all falling into your hands.“Spiritual Energy Resurgence” version: You nurtured “Mountain Spirits and Wild Creatures”: Twin lotus make you invulnerable to both water and fire, the Seven Star Sword cools the light across Nineteen Provinces, Parasitic Species feeding on living beings, Void Species rooting in the void to absorb the Spiritual Energy of heaven and earth... You established an inner scenic area, cultivated immortal species, with “Grand Taiyi Lotus” replicating en masse! “Ancient Tree of Life” immortal and indestructible!“A true seed falls into the Dantian, can nurture spiritual sprouts for ten thousand years, one day when the cultivation is complete, my life is governed by me, not by the heavens!”“Heart fire shines like the sun, kidney water is the source, spleen stores earth, lungs refine through metal, liver sustains with qi. Using the body as the foundation, nurture original species, foster all laws, achieving the status of Shennong Dao Master !”

The boy who Sneaks in My Bedroom Window

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.