So you want to build a
street rod. You've found a nice solid body from a '57
Crown Vic. You've even got a dash too, though perhaps the
boll weevils have gotten into the upholstery. No matter, it all will get thrown away before you're done.
Thing is, like a whole lot of cars from the forties and fifties, the Vickie started out as a sensible, family sedan. It's a very tall car, with a lot of glass. And the really cool cars aren't tall like stilts, they're low and hug the road. Now that height has it's advantages. You have enough headroom to accomodate Shaquille O'Neal. Only, you're just 5'10" yourself, and Shaquille isn't a very likely future passenger. The headroom is overkill. You can lower the car some by changing tires and lowering the suspension, which you were probably going to mess with anyway. You might even want to lower the body itself.
Time to chop the roof down some.
All you need is a sawzall and a welder. A car's roof is held up by a number of pillars, really metal places that tie the lower unibody to the roof. To keep the pillars straight, you letter them with the frontmost pillar-- the one by the windshield-- being the 'A' pillar, and moving back from there to the 'B' and so on. To chop a car you cut sections of metal out of each pillar and then weld them back together again. This lowers the roof.
Sounds simple, right? It is simple in concept, but the execution is everything. The job would be simple if the pillars were all perfectly straight and plumb. Which they are not. On most cars the pillars slope and change in width. They may be curved. They may have bracing behind them. All this has to be matched up, and smoothed perfectly.
This is where the art comes in. You need to not only have a welder, but be really good with one. In unit body cars, those pillars are structural, as they help replace the frame. Roofs stiffen the body, which is why a lot of convertibles shake, or are heavy with additional bracing. Your Vickie is body-on-frame so you don't need so much structure, but still you need to get this right if you don't want to crack windows. Not to mention having it look good. The welder may have to fill gaps. Some curved metal pieces whil have to be reshaped. You may use some lead body filler, or melt in steel. You'll have to reshape the window seats. And then grind it all perfectly smooth. Chopping a car takes lots of time. Or money. Say, ten thousand US dollars. Or more.
And then there's channeling which is where you 'adjust' the body floor in order to accomodate the lowered ride height. Meaning you have to raise the floor, because when you lower the body things like the driveshaft, transmission, suspension, and so on get in the way. You think the chopping part was hard? It can be done with a unibody, barely, but that requires refabricating the entire car. It's doable with body-on-frame cars like the Vickie, but a challenge. Remember, you've got a frame to cope with as well, and you want as little as possible intruding into the passenger compartment I have no advice here, except to tell you that every car is different. At the very least you'll have to alter body mounting points. Skill in fabricating and patience matter
If you do it wrong, and your car will look like Quasimodo. You won't be able to get a windshield to fit. One good idea is to cut down photos of your car, and scale so you get the proportions right. And by the way, your glass has to all be custom made, including the window guides and trim. But if you do get this right and lay on half dozen layers of pearl white and candy apple red, your '57 crown vic will look like a low, lean, road eating machine. And you'll feel like Shaquille O'Neal in your now snug passenger compartment.
Sleek appearance explains why a number of vintage and modern street rods have been chopped and channeled. Properly done it makes the car look a lot racier, at the price of headroom you can partly get back by replacing the seats. Cuts the frontal area quite a bit too, for lower drag. It's vintage as well; lots of cars were chopped and channelled back in the day. Can't see a Sha-na-na concert without one.