That wasnt a lamborghini prototype.
^1991 Cizeta Moroder V16T
Apparently, people say they made an earlier prototype and sold the concept to lambo.. but seriously, besides the front.. the car is very different to a diablo. So its not like they were being unoriginal.
As for the engine.. Why? unless they stupidly keep adding more and more engine capacity with each generation of car (countach lp500 5.1, doablo 5.7, diablo 6, 6.0, murcielago, 6.2)
I dont see why they need to go further there either.. what they need to do is get the most out of an engine.. say 650bhp for the murci's engine.. and focus more on reducing weight rather than increasing it.