I want to build a Bushmaster and need advice as to what I'll need (that I don't already have), where to get it and approximately what it will cost.
I already have the following:
A good lightly used 20" A2 barrel
Lots of 20 and 30 rd. magazines
The Army/USMC maintenance manual for M16A2
M-16 cleaning kit
Big-assed bench vice
good start. some folks would start with only a pair of needle nose pliers and a kitchen table, so in your case, you've got a great start.
now, ditch the barrel and order yourself a complete kit from bushy.