What make of car was the first to have a V-8 engine ?

The Rolls-Royce V8 Legalimit was produced from 1904 to 1906.

The Rolls-Royce Legalimit with its 8 cylinder engine, the cylinders being in a vee, was to be as silent as an electrically powered town car.The crucial feature was a gearbox layout restricting the top speed to the legal limit of 20 mph. - The History of the Automobile.

The company became the first to make a mass-produced V8 engine, a 35 hp 6107 cc CJ unit in 1910 and 3534 cc Type CN a year later. - http://en.wikipedia.org/wiki/De_Dion-Bouton

A full decade after Britain's 1904 Rolls-Royce Legalimit, Cadillac produced the first American V8 engine, 1914's L-Head. It was a complicated hand-built unit with cast iron paired closed-head cylinders bolted to an aluminum crankcase, and it used a flat-plane crankshaft. - http://en.wikipedia.org/wiki/V8

Rolls Royce was the first to produce a V8. De Dion-Bouton was the first French company to make a V8, and the first company to mass produce them. Caddilac was the first US company to make a V8.