Not a lot.
As with so many of these replicas, it relies on a donor vehicle of much later vintage, for running gear and invariably, engine/transmission.
So all you really finish up with, is an exterior look-a-like.
(Same with all of the Jag C type and D type creations: they use much later XJ6 engines, suspension etc. Not the same at all).
I did quite a bit of work to a DB4 Superleggera in 1968, belonging to an ex Ford Europe colleague. Which entailed driving the car when finished for testing and final tuning.
The whole ethos of that period of Aston was a combination of the wonderfully crisp power from the classic straight six twin OHC and the almost truck-like gearbox!
The later six in the DBS was somewhat more refined.
Worth recalling two things about Astons of that era.
First, the straight six TOHC engine had originally been designed by of all people, W O Bentley, when he was working for Lagonda cars; Lagonda went into receivership and the assets were bought by David Brown and added to his Aston venture.
Second, David Brown was mainly, a manufacturer of truck transmissions: and he insisted that Aston used his gearboxes!
So the period Aston had a sort of raw surging power from a racing heritage straight six and a pretty slow gearchange!
All that said, however, the short chassis DB4 GT was the first "production" car to achieve 0 to 100 MPH and back to nought in less than 20 seconds!
Thanks to Girling disk brakes.
Pretty to look at and pretty impressive to drive them!
I drove a later DBSV8 for a fortnight, which one of my wealthy clients wanted to sell. It was only six months old, no mileage and he'd already bought a new Rolls Shadow, 'cos he found it hurt his back getting into and out of the Aston!
Nice car, but not the instant pleasing heritage of the earlier cars.
Nice site here:
http://www.donrose.com/DB4GT-LW.html