i think there are a whole lot more factors that come into play than you may realize...i thought about doing this only with some sort of a hatch car but once i sat down and thought about it, its not worth it at all.
heres a few things you might want to think about...
how do you plan to shift the trannys?
how do you plan to syncronize the the motors/trannys? if one motor is turning even slightly faster than the other then thats just a completely wasted motor and all it is is extra weight.
how do you plan to supply fuel?
what are you going to lay the fram out on? pen and paper dont woek unless your a good draftsman. i got 99% in 4 semesters of honors drafting and wouldnt even take on the task.
how about all this bending, measuring, welding, measuring, notching, measureing, and oh yea...measuring?
you know to make everything as triangulated as possible right?
what kind of metal will you use?
if you use anything decent (cromoly or DOM) you know your gonna need a TIG welder right?
have you priced metal lately? japan screwed everyone on that one.
trottle?
clutch?
and these are just a VERY few things to take into account. there are countless other things such as suspension, how your going to mold or shape the body depending on what you plan to use (glass or metal).
im not trying to put your idea down as others have said its been done and made to work pretty damn good. tho i do think its a little more than you or anyone on this board for that matter could handle. im just trying to to put the ordeal into prospective. every year manufactures as well as independant racers spend countless hundreds of thousands of dollars on up into the millions(a piece) trying to devlope new and cutting edge race cars. even if you did all the work yourself...you better be ready to dump damn near 100 grand in this project dog...