Miele makes a 42" electric cooktop, its available for the US market. Its in their MasterChef collection, model KM 452. Its 42 inches, 9 burner, 7-cooking zone cooktop.

Not sure if a link placed here will work, or if its okay with the current rules.

Here is a link: http://www.miele.com/usa/cooking/cooktops/product.asp?nav=21&cat=3&subcat=11&series=12&model=79

otherwise visit their website, it is miele.com there you can source local dealers.

Another thought is to use a miehle "combiset" system. This allows you to customize your cook-zone with plug in units including barbecue zones, deep frier/boiler zones, griddle zones, as well as ceramic double burner zones. They are series KM400.

http://www.miele.com/usa/cooking/combisets/product.asp?nav=21&model=84&series=13&subcat=12&cat=3

Jenn-Air makes a 43" downdraft cooktop which has four burners and an integril grill assembly.

CVEX4378 W or B for white or Black In their expressions line.

You didn't mention the exact opening you have, nor if you need a downdraft system, so I'm guessing here.

The miele 42" cooktop is about 21-1/2" deep opening, the miele componants you could enlarge to 43" for four units of your choice the units are 19-1/2" deep.

Am unfamiliar with the specifications of your brand/vintage cooktop and have no model number to try searching what your present conditons (cut-out, unit depth and electrical zone specifications) might be.

meant CVEX4370W or CVEX4370B

You can purchase your choice of cartridges seperately, so if you want six burners and no grill you can do so.

This one is a bit wider than 42 finished edge so they round it up to 43" but it might still fit in your opening, or require a miminum of retro-fit work.