One of the rarer classic Lamborghinis, the 400 GT "Interim" is the result of production evolution during the manufacturing run of the 350 GT. As the 350 GT was nearing the end of its production run, Lamborghini developed a larger, more powerful version of their 3.5L V12 engine. This engine found its way into twenty-three 350 GT bodies. Although billed as the 400 GT, these "Interim" cars stand apart from the later 400 GT 2+2, not only in design and powertrain, but in rarity in the market.