there is no way 3.91 will hurt its time it will only help it. it helped the 1le it will help the z/28.
the origianl z/28 sucked at the quarter mile becaue it had a 302. this one has a 427.
I think if the 1le can do 12.7 or so the z/28 whould have no problem with 12.2-12.3 at minimum.
the power difference betten the LS3 and the LS7 is night and day. the LS7 smashes it everywhere low end, top end, more rpm range. I have owned both. stock vs stock it has some much more power.
2013 ZL1 (president of the tangent oregon trophy husband association, founding and only member)
2013 Megacab 8" lift 38"mt's