Indeed, lowering the seat can solve the headspace problem of virtually any car. Lightening the driver's seat (if the donor car has powered seats, for example) may be necessary anyway. Considering my purpose for the car, the back seats will simply go, to make space for batteries.
George, you aren't wrong about diesel fuel efficiency, although in Canada, diesel is more expensive than gasoline. Only about 1/2 of the fuel stations carry diesel around here. The choices of car from the OEM are limited, seemingly, to Volkswagens and their tarnished reputation, and trucks larger than 1 ton. I have already considered other fuel conversions, such as natural gas, but there are no businesses offering the conversion in Canada or a home fueling station (I have NG service at the house) and the economics seem to save me very little money. The cost of the conversion itself won't be recovered for years. To rephrase my goals, I am trying to USE NO CHEMICAL FUELS at all.
I started to figure out what to expect from an EV, bearing in mind that I want to go minimum 50 miles, preferably 100 miles, on a single charge. I collected stats from the EV's on the market (Ford, Chevy, Mitsubishi, BMW, and, of course, Tesla) and they were very interesting to compare. The first thing I noticed (and it's obvious on the graph below) is that the Tesla's are in a class all their own. Basically, a Tesla gets 3x the range of any other type of EV available for sale from a major manufacturer. The green dot near the red Tesla dots in the Chevy Bolt, closing in on Tesla territory. Most of these can meet my minimum range, but few of them can do more than 100 miles (Chevy Bolt, BMW i3, all Teslas). Price of admission into the long-range
EV club starts at 40,000 CAD.
Looking at vehicle conversions, I got more surprises. Would you believe that there are many auto conversions on the DIY EV forum and EV Album that have BETTER range than the OEM cars on the market? I was encouraged to see that. Admittedly, these are just builder claims, not as scientific as CAFE test trials. But I don't expect that the OEM claims are exactly what I would get either. Temperature always affects battery range, so I'm more likely to believe the range claim of a DIY builder in Oregon state than the OEM official numbers from California as representative of range in Calgary.
LiPO cells make all the difference in DIY conversions. Compare the LiPO conversions to the lead-acid battery powered cars, and there's no competition. There are plenty of LiPO battery conversions that meet my minimum range requirement. Looking more carefully at the examples that do, and I find some other things in common. Two of them are Honda Civics, converted using Advanced DC series-wound motors. To get the range they obviously need to a LOT of batteries inside. Apart from that, I can't see any other components or equipment that have strong advantages. So I think a lot of choices are wide open to me, to use use what I think I need as I dig deeper into the design.
I was expecting to see some kind of advantage, given all the claims being made, for the AC motor conversions. No sign of it in the numbers I collected of DIY EV's. I doubt that AC regeneration braking will help me, since my goal is to run on highways, where I tend to not touch the brakes for 10 - 20 minutes at a stretch. That is one cost and complication that I can avoid.
Warpspeed - that's a neat idea. It brings up another way to choose a candidate for conversion - saving a rare auto from the wrecking yard. Plenty of cars go to scrap for the simple reason that their engine quit and isn't worth the repair. This appears to be a factor in the number of Mazda RX-7 conversions out there. The average shop isn't interested in tampering with those funny engines, and owners are stuck with big repair bills.