A few bits to think about...
I agree with others that the McSorely +2 and +4 chassis designs are probably better than going strictly "by the book". Even though the "book" chassis is a tad larger than the original 7, it's still on the small size for most adult North Americans. I'm a tall, and fairly slim male - I got into an original '60's Lotus 7 once...and had to be lifted out by friends - I couldn't get out on my own, as I was wedged in there. Plus, it was so short in leg room, I couldn't possibly have driven it.
I know most here advocate using a single donor car as your parts source, but after much deliberation, I elected not to do that. Why? Because you are forced into a lot of compromises, trying to make parts fit into a car design completely foreign to the parts' original parameters. Yes, in the long run it IS cheaper...but not necessarily by much. In my case, the cost difference wasn't enough to justify the compromises I'd have to have made.
By choosing to build without a "one donor car", I've been able to collect the absolute best possible fit for parts, from many sources, so as to virtually eliminate the need to compromise on my finished car.
For example, if I'd used, say, a Toyota as a donor, I'd have felt compelled to use the pedal assembly, regardless of its utter incompatibility with the design I wanted. Ergo, compromise, and a lesser product than I desire.
This is not to say that I've bought everything new - far from it! Most of my parts have been sourced from wreckers, online used, garage sales, local used parts sellers, etc., so the overall cost has been very reasonable. In some cases, though, where I had very specific needs, I've bought brand new parts where their application precisely meets my design, and no used wrecker-sourced parts would do.
The aforementioned pedal assembly example is one instance of this. I saved my shekels, and bought a full set of Wilwood floor-mount pedals & master cylinders. Really not particularly expensive, as it turns out, and they meet my design wishes precisely. Plus, they're brand new, and the best available. It's a part where I wanted NO compromise, and that's what I got.
I'm somewhat biased, in that I have a strong desire to stick to the overall look of the original Super 7 Mk. III, as I'm a bit of a traditionalist. Aside from outside dimensions (which are proportionally very similar, but a little larger so it fits me), a description of my car reads exactly like the original 7 Mk. III (Ford 4-cylinder DOHC engine, Weber DCOE carbs, live axle, etc.), and it looks like one, too. While the engine, etc. in my car
look original, they are 21st century stuff.
When it comes to the rear suspension, you'll hear a lot about IRS. I looked long & hard at it, and in the end, went with a live axle. I just re-read Des Hammill's book on suspension design & tuning, and it confirms my decision. He basically concludes that while IRS is a laudable goal, in reality there's little gain in a car as light as a Locost, particularly in light of the added weight and complexity (this, referring to cars that are intended for primarily street use with occasional track days; for all-in race cars, IRS is generally preferred although, even then, live axles still work well).
When I started my build, the cost of going IRS was, in these parts, enormous, and sources were rare. Hereabouts, even a totaled Miata cost huge money, and a rear suspension from a wrecker (when you could even find one) went for thousands of dollars.
Conversely, my Mustang II live axle cost me $100, it's foolproof, and it's lighter than most of the IRS setups available to us mere mortals.
Long story short - don't feel obliged to follow a specific path. Consider WHAT you'll be doing with the car (A pure race car? Strictly street use? Fun sports car with occasional track day use?), whether a single-donor will provide the majority of the specific parts you want for your intended final result, and what your budget will be (on the latter, you'll find that this will likely end up...um...a little optimistic!). There are a TON of options available to you, so balance what you really,
really want to end up with, tempered by the extent of your budget, and you'll be very, very happy in the end!
Just my $.02 worth...and, welcome to the madness!!
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Scratch building, at continental-drift speed, a custom McSoreley-design framed, dual-Weber 45DCOE carburated, Zetec-engined, ridiculously fast money pit.
http://zetec7.webs.com/