Dungeon Diver: Stealing A Monster's Power - Chapter 756

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.

Karl transmigrated into a new world, and once he reached the age of 18, the day of the profession awakening ceremony came.In this world, your strength and profession determined everything about your life, with no second chances.And with nobody to support him, it was make or break for Karl.Yet, once his turn arrived, and he closed his eyes...He woke up in a strange and unfamiliar place.[Welcome to the Spirit Cemetery]A skeletal figure appeared before his eyes: it was death, revealing itself to him.“What the...”But before he could even understand the situation he was in, he heard a notification.Ding![You have awakened the EX-Rank profession “Spirit Summoner”][This is your Spirit Cemetery, find a way to fill it.]

Dressed as [fantasy world] [patriarch], portray the fantasy world as realistic as possible from the perspective of the family, grow spiritual fields, raise spiritual fish, develop various family industries in an all-round way, support salted fish elders to become ancestors to serve as umbrellas, and inspire juniors to bravely venture The Holy Land Academy has come to the fore.

It is not a fantasy of passionate combat, but is based on the promotion of various family industries, capital, facilities, domestic servants, family generals, clansmen, guest officials, in-laws and other elements. Trying to see the “old-fashioned” fantasy world from a fresh perspective.

- Description from novelbuddy

After she noticed she was being chased after by a certain beauty, she bound herself to a System and started her quick transmigration journey…

After a countless number of worlds, the beauty was finally driven to villainy, and his long, elegant fingers pulled at his black tie…