I use the adjustability of the doors, fenders and hood so I get equal gaps on both sides, sort of an eyeball thing. Start with the doors and establish a good usable gap between the trailing edge of the door and the front of the rear panel so that the door opens and closes perfectly, then the cowl but don't lock it down, keep the bolts finger tight, then the hood. Keep the hood open while you put the fenders and sugar scoops on, then very carefully start lowering the hood looking for possible contact with the fenders as you lower it. Once the cowl, fenders and hood are on you start doing minor adjustments until the gaps are as equal as possible on every side. That's just how I do it, others start at the front and move back to the door gap.