Who can honestly say that they haven't sometimes wished for a little more reliability, a touch extra power, a rather less conspicuous fuel consumption from their classic? who hasn't, even in a single moment of disillusionment, idly considered the appeal of a car with looks and character of a classic but with the engine and transmission of a modern car?

Most of us will then dismiss those thoughts, whether for reasons of originality, cost or perceived bad taste. But a rising band of owners and specialists across the world are switching their machines to the latest running gear to stunning effect. These two - Elan and Frogeye - are typical.

Do they work? Is it okay to mess with time honoured designs? The second question is for personal opinion and intelligence, because it would be very wrong to rip a properly historic car to pieces. So here comes the answer to the first question...

I starts several days before our photoshoot, when we take delivery of the Elan from Spyder Cars, part of an engineering company that's been builing replacement chassis for Lotus models since the 1970's. The Elan turns up the rorty zing of blipped throttle, then sits idling at a perfect 800rpm as i'm shown around it. I desperately want to lean in and switch it off, for fear of it overheating. (I didn't need to worry.)

Under the pretty glassfibre there's a Spyder replacement chassis, spaceframe instead of original pressed steel, and in that sits a Ford Zetec engine from a Mondeo. Running throttle bodies and ECU, but otherwise standard, this pumps out 175bhp without problem. Mated to that is a modern Ford five-speed gearbox, differential and brakes, plus the latest coilover suspension. It's not for me to try to second-guess Colin Chapman, but i'd like to think he'd approve. 

I've got the Elan for two weeks. The Frogeye, though, will be a more abbreviated pleasure. There's just a day to sample its 180bhp K-series engine and five speed box, but that promises to be amusing because it's in the  care of its creator, Tim Fenna of Frontline Spridgets, who's been modifying Sprites and Midgets for over a decade. And doesn't hang about.

Five years ago, I drove another of Tim's creations around a cold, wet Knockhill circuit and loved every minute of it, and i've also tried a full line-up of his modified Spridgets, from mild to wild. But the Frogeye promises to be one of his best yet, being a joint indulgence of both his and an affluent customer.

As for the Elan, this is the third Spyder creation i've tried, but the other two were Elan Plus 2s, the raison d'etre of the Spyder conversion. The logic goes like this: Plus 2s are, relative to 'proper' Elans, unloved and under valued and yet they cost just as much to rebuild. So there are plenty sitting around with rotten chassis, in need of a £5000 engine rebuild, and maybe a few thousand more to spent on transmission, suspensions and brakes that just aren't economically feasible to sort out. A good one will go for as little as £3500.

So along comes Spyder and develops a kit that includes a modified version of it's spaceframe chassis (to take either original running gear or modern Ford bits).  

Spyder Cars Zetec Elan

Engine

1989cc, four-cyl, 16v, DOHC, jenvey throttle bodies, Emerald ECU

Power

175bhp @6700rpm

Torque

147lb ft @ 5300rpm

Transmission

Five - speed manual, limited - slip diff

Suspension

independent, upper and lower wishbones, adjustable coil - over damper units

Brakes

Discs all - round

Weight

863kg (1898lb)

Performance

0 - 60mph 5.5 sec top speed 135mph

Value

£20,000