You may be correct as I am no Lambo expert. I guess a safe redline depends on how brave,rich, or stupid one is. I read some where that Bizzarini claimed with some upgrade you could turn 11k rpm Yikes. I would be more inclined to believe the 8k number especially for a stock motor which is still not to shabby.In it's most highly tuned form (Miura SV) the 4 liter engine was claimed to make 380 at 7,800. Many people scoff at those as being "italian" horsepower, however, including, I believe, Bob Wallace himself. Safe redline was no more than 8,000, I believe, and that was accomplished with very stiff valve springs. So I don't think you're going to get XJ-13-type horsepower that way, although I will defer to Chad on that. He definitely knows his Lamborghinis.
The lambo motor is out of the budget right now but fun to think about. I believe my current engine will give me more than I need for this car. I think if one were to stick a nice stock 5.3 V12 engine in this car it would scare the daylights out of almost any other road car.