Nah, the offset is pretty good, they'll fit just fine without having to jack it - they came from a certain '68 Gibb/Harrell Nova!
The extenders on top of the air shocks does work though, (along with shackles), as I did it to get my L60's to fit on my first Nova. Nobody could ride in the back seat either, had plenty of slices in the L60 sidewalls!
Ooops, this pic is with the 275 radials, the rims were Ansen 15x8's with a lot of offset to the outside!