got a question, welding a new 4spd tunnel......

Well; If you have it in dead nuts-how can you tell?If you are just welding in the hump,just make the top level and fit the hump to the floor.If you are welding in a complete tunnel with the hump,it has to fit the firewall and the driveshaft hump.It really isn't rocket science,I have welded quite a few but I'm not really sure any were"dead nuts"