The 4.0-litre naturally-aspirated unit produces 373kW of power and revs to over 9000rpm, which puts it on par with the latest water-cooled 911 GT3.
Modifications include a carbon-fibre resonator chamber and air-box that will be placed on top of the engine. To help with cooling, the cabin will have an intake system installed, and mounted air rams on the rear side windows.
The new powerhouse is actually based on a 184kW 3.6-litre engine out of a 1990 911, and after all the modifications, it will most likely be much lighter than the original too - with magnesium, titanium, Inconel and carbon-fibre parts to help reduce weight.
Hans Mezger, the legendary Porsche engineer, has helped oversee the project as a technical consultant, while Singer's founder, Rob Dickinson has expressed his excitement over the venture.
"Singer is delighted to be working with Williams Advanced Engineering and Hans Mezger to offer our clients a 'next level' of restoration and modification services for their Porsche 911s," Dickenson said.
"With careful and dedicated development, this iconic air-cooled engine has much to give both its existing devotees and a generation of new enthusiasts."
A long-time client, Scott Blattner, has commissioned the project, which will see the engine set into the rear of a 1990 911.
More details will arrive in September when the car will be revealed.