Yo dude.
It's worth spending the time to get it right, as the cam is the 'brain' of your engine, and it'll all just end in frustration and dissappointment if it doesnt perform as you expect.

The total duration is pretty meaningless, it's just impossible to accurately state where the valve starts opening,. you really need to either ask the cam grinder where to set the thing up at (inlet fully open at XXX degrees atdc) or get the specs at a fixed lift (usually 050 thou) and derive where full lift should be.

You really need a dial guage (the afforementioned DTI) and a degree wheel (like a big protractor). You can then set about finding out exactly where top dead centre is, and where the cam's happening at!
You then need some way of adjusting the cam timing (I suspect that Erol will be able to source you an adjustable sprocket)

A little time spent now will be worth it, and hey, you'll learn a heap which is never a bad thing!