Has anyone here custom made a car with a sequential gearbox from a motorcycle and mated it to a car engine. I want to do this because i want to put a sequential gearbox in the car i am going to make but those kinds of gearboxes for cars are very expensive and i doubt I'll be able to find one in a junk yard. any help would be apreciated.

Use a motorcycle engine with a motorcycle tranny.. small, one passenger car with no luggage right? You'll need a big engine because it'll be bigger and heavier than a motorcycle, but I don't see any reason to use a car engine.

A motorcycle transmission is designed to handle the torque that a motorcycle engine can produce. Most car engines can produce a lot more torque. You'll bust it as soon as the tires get traction.