The accelerator pedal on the E450's are "fly by wire", which means there is not a throttle cable. They use a Potentiometer built into the pedal assembly to send an electrical signal to the computer to control the throttle. Basically, what I'm saying is you cannot just replace the pedal assembly with another style. Several companies do make add on pedal covers that can increase the width of the OEM pedal, just google search "Throttle Pedal Covers" . I would caution you on adding a cover though, worse case the cover interferes with the engine cover and sticks because yes, it's very close and narrow from the factory. You cannot modify the engine cover by cutting it as it fits a specific cut-out in the floor. I would think after some use, your husband would get used to the factory pedals, I know I had the same concerns and have adjusted to it. Good Luck !
