Chongfei Manual - Chapter 82

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

A normal office worker, Toru Minasuki, was swallowed up by a dimensional fissure and reincarnated into a different world. Upon reincarnation, Toru was given a [skill board] by God. Make the most of it to acquire all the necessary skills! Even though he is an “inferior person,” he’ll make his way to the top!

Heartbreak comes with perks?Gao Fei was devastated and nearly fell apart after being dumped for being poor, but he unexpectedly received the Demon God Heritage.From that moment on, he could easily gather wealth, beautiful women, and power all into his fold.What?Now his ex-girlfriend is on her knees, begging him to come back?Sorry, do you think you're worthy?

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.