Im pretty far along with my G3 build. it's my first build. I just got mine November. The last FFR part just showed up Thursday. I was surprised that so many major roller parts were backordered for so long. I got my IRS parts in Feb. The steering rack same time. the AC and PS parts and Exhaust just showed up this last week. The IRS not coming held me up quite a bit I couldn't finish the roller and order wheels with out all of that.
SO be patient.
Take a look at my build thread.
I returned a pile of parts from the complete kit to get a refund.
I went with the same headers after doing the shorty ones.
I am doing a variety of custom parts. I used 2015 Mustang 6 speed. 2015 brakes front and rear. custom headlights, mirrors, ac vents, shifter, and dash. I went with the front splitter and rear wing. I went the PS and AC and Coyote route.
Enjoy the ability to make it yours. the hardest part BY FAR is choosing your color. I finally thing I have it figured out but I have been driving through car dealerships and large parking lots taking photos for MONTHS.