that they are very much the same motors so it should fit, physically. you would want to be careful with all the electrical connections and controls though. it would be a good idea if possible to start with two complete cars so you could switch everything that is different.

also the 500e has some reinforcing in the chassis that the 400e may not have so if you are going to use the 500e motor you may have some chassis flexing issues. i dont know specifically what will be different though.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.