A close friend of mine has ran multiple 240z's in the 10's/11's with Small Block Chevys. His cars were updated with poly busings, solid front diff mount, welded diff, roll bar, tokico springs, tokico cartridges, 15x8 welds on the rear with 26x9 slicks, 15x4s on the front.
One of his can be seen in this DNI video from 2009: https://youtu.be/DXj573SiU58?t=2m49s
He technically needed a full cage for the times he could run. And he could have benefited from strengthening his frame rails and adding subframe connectors.