I am in the same boat. Replacing my second Jennair, --maybe I should just keep it? Can not help you too much. what I have been told, is that the size of the ductwork will be different. Depending on the space and the size of the ducts in the new system, you could be looking at trouble. Either that there will not be space in your cabinet or under the cabinet, for the new size of duct. Or expensive work, and frustrated installer having to go out to buy the right attachments. SO I am going to dig out my old Jennair materials and take that with me to a dealer to see what best matches it. Maybe even photograph what is under your current cooktop and downdraft. One dealer told me it washighly likely that the new downdraft would have totally different sized ducts. The point is that Jennair was pretty ineffective, and the new one might be better, but trouble to install. You may need to replace the ductwork.

While it's a little hard to tell your exact configuration, you may be able to use modules to fill the space, with SS fillers if (when) it doesn't fit exactly. What may be a larger issue is the duct size required for an effective 48" downdraft, which would be at least 8" and probably closer to 12" versus what's currently in for the Jenn Air (ours 20 years ago was 4"). You may want to consider an external blower. I have cooked on an induction cooktop with a 1200cfm downdraft (15" riser) with an external blower and I was impressed by the quietness and the volume of exhaust it moved. Certainly not as effect as an overhead hood, but still seemed to clear pans on the rear burner, and looked rather cool. Such a config would probably be deeper than your current Jenn Air so you would have some additional installation work. Also be advised systems like this are not cheap.

Basically remove all the down draft venting that's in the way and seal up the vent. If you put in a over the range hood you can us a recirculating hood since you most likely do not have a vent pipe above the range.

1a. You originally wrote "stove". I guess you meant "cooktop". Here are two Frigidaire induction cooktops that are about the same size as your current ones. You'd have to measure the size of the cutout to be sure. Any downdraft vent is not built into the cooktop. Frigidaire FFIC3026TB 30 Inch Induction Smoothtop Cooktop Frigidaire FGIC3066TB Gallery Series 30 Inch Induction Smoothtop Cooktop 1b. Downdraft electric cooktop: GE Profile PP9830DJBB 30 Inch Electric Smoothtop Cooktop (not induction) 2. If you really meant "stove", then there is ONE downdraft electric range but it is NOT induction: KitchenAid KSEG950ESS 6.4 cu. ft. Downdraft Slide-In Electric Range with Self-Cleaning Convection Oven in Stainless Steel