I'm looking to build a complete upper, for a lightweight build here is a list of my preferences: Upper preferably A1 style, A2 is acceptable. Barrel, 16" pencil barrel contour, dissipator style so I can use a rifle gas system. I would prefer m4 feed ramps. 1/7 or 1/9 rifling preferably. Standard A1 or A2 style front sight base, parkerized finish. Are these combinations compatable? If not, what substitutions would need to be made. Who would be the best sources to buy the parts from?