The 737 rides significantly lower. Check out the 737-700/800/900 series and you’ll notice the engine cowl (inlet) is not perfectly round at bottom because of gr

The 737 rides significantly lower. Check out the 737-700/800/900 series and you’ll notice the engine cowl (inlet) is not perfectly round at bottom because of ground clearance. This is likely a design choice leftover from the original 737 series that used JT8D engines which are turbojet engines rather than high bypass turbo fans that make modern airliners efficient. Because Boeing has been so set on retaining the original type certificate they’re restricted in how much they can change the airframe. The only way to slap bigger more efficient high bypass turbo fans was to move them forward and up.