Alfa Romeo Spider and next-gen Mazda MX-5 details

Details on the new Alfa Romeo Spider continue to come in. Alfa sources say the car will blend lightweight engineering and modern styling with an accessible chassis and power output around 170 hp. It will go on sale in late 2015, sources said.

Based on the next-generation Mazda MX-5 platform, the car will be built in Japan, and the new Spider's styling is understood to be close to finished. Maserati and Alfa design chief Marco Tencone oversaw design development, with his team working out of Fiat's Centro Stile and a temporary satellite studio in Japan. Most clay model development and design detailing is happening in Japan, which is unusual for an Italian company.

Tencone's most recent designs are the fresh new Alfa 4C, and the handsome new Maserati Quattroporte and Ghibli. Pininfarina designed the original boat-tail Duetto in the mid-1960s but is not involved despite creating the striking 2010 Duettottanta concept. That car was shown as a celebration of 80 years of Pininfarina and blended the original's slender boat-tail proportions into a more modern look. Alfa didn't buy rights to Pininfarina's design but sources in Italy say Centro Stile tried for months to make the design work on a production car.

Sources also say Tencone will take a similar approach on the new Spider -- looking at historic design themes but with a modern interpretation, as the 33 Stradale has been re-imagined for the 4C.

“The new Spider definitely won't be retro in design,” one said. “The Spider has to be contemporary and must fit into the range with the modern 4C.”

Another source adds, “It would have been easy to go for a retro, boat-tail type design, but how would that fit in with the 4C and today's modern Alfa designs?”

In previous interviews Tencone has talked about Maserati and Alfa design in terms of “original ingredients” and the way '60s Italian industrial design didn't “interfere with the function of the products.”

We hear the Spider will have conventional headlamps, and Alfa hopes this will give the car wider appeal than the hard-core, mid-engined 4C, on sale later this year. Recall the 4C features a single projector headlight, five circular LED running lights and an indicator bulb set in a contrast-colored composite molding, giving it a menacing face.

The Alfa shield grille will dominate the front end and there will be lower air intakes but the execution will be more subtle than the 4C's.

Alfa and Mazda will share the windshield and frames, front bulkhead and engine compartments as well as front and rear axles. The cars will be about the same size and weigh roughly 2,200 pounds.

The two cars will share structures to keep costs down, but sources say the exteriors will be completely different and in fact no body panels will be shared. Overall common parts will be around 40 percent.

The Spider will also use its own engine. Just one size is being engineered for launch -- a version of the 1.4-liter, turbocharged Multiair four. U.S. versions will have about 160 hp. The engine will be mated to a six-speed dual-clutch automatic transmission.

The Spider will be given its own chassis tune once development work starts. Alfa wants to give the car suspension settings focused on everyday driving to distinguish it from the more hardcore 4C. Sources say the chassis tuning hasn't begun yet. “We are concentrating on the 4C at the moment.”

It also looks like the Alfa and Mazda will be launched separately. The Mazda is slated for an early 2015 reveal, possibly at the Detroit show, while the Alfa could be held back until Frankfurt that fall.

By Julian Rendell