Having run A body stock eliminator cars for years, I ran the 6 cyl bars.83 in the beginning. When the .810 bars became available I ran those with a double adjustable shock. I am a many time NHRA record holder with 340 manual shift stockers running high 10's with a low compression 340. Use the smallest bar and a good shock. This works best if you have good rear suspension. Oh and remove or disconnect the sway bar at the track.