Have fun Alf
I don't know if you have built one before but I thought the biggest SOB was the pivot pin retaining spring and detent, Watch your eyes with that one as it WILL go ping on you.
[Guess I didn't "post" my last reply]
Anyway, I'm aware of the detent spring problem. A friend of mine, a weekend dealer, is making me up a lower kit, springs, pins, Timney trigger, safety, magazine catch, bolt hold-open, AND EXTRA "little pieces".
Next will be the stock. Gotta start looking at what's available and start saving the pennies again.