While Lamborghini went out on a limb with the design of the Miura, Ferrari, as its usual practice, played it conservative. Their flagship road car at the time was the 365 GTB/4, popularly known as the Daytona. While it was a departure from the styling from previous Ferraris, it held on to one convention: the engine was in the front. While Ferrari did produce a mid-engine car - the Dino 206 - it featured a low powered six cylinder engine. A high powered mid-engine car was an unknown quantity and many were concerned that the extra handling afforded by that layout combined with lots of horsepower would be dangerous and unwise on the street. Enzo Ferrari himself was said to have been in favor of the front engine design because tradition always "placed the horse in front of the chariot".
After the 365 GTB/4 (and it's successor, the 365 GTC/4) Ferrari did go mid-engine with their high powered offerings, starting with the Berlinetta Boxer which featured a flat 12 cylinder engine. How much the success of the Miura had to do with this change of policy is not known.
Lamborghini and Racing
Ferrucio Lamborghini had a strict no racing policy. The reason most often cited was that he did not want his son Tonino to be involved in the dangerous sport. Despite the policy, much of the engineering staff had a strong racing background. The Miura V12 engine, as conceived by its designer, was originally intended for use as a Formula One engine.
The closest Lamborghini came to racing (at least during the Miura production years) was the creation of the special Jota. A few private efforts were undertaken that involved the Miura, but none of them were noteworthy. All during the life of the company racing has been hinted at, with the most notable effort being a Formula One engine program in the late 1980s and early 1990s. Even today there is discussion of the possibility of an F1 effort, should production of the road cars reach a certain level.