the engine i'm getting is a 2lr twin cam sierra engine? is it 16v or 8v?

It depends.. 8v was the most common, if it has a distributer on the top left of the front of the engine and a black plastic cam cover it's an 8v.

Far more popular route would be to fit a SOHC Pinto 2ltr. Far better potential for tuning, lots more aftermarket support for spares etc and considered a far better bet for kit car use. If you want twin cam go for later Vx or zetec engine.