Get the big chassis. At 6′ 180 you’re at the max driver size and weight. Don’t listen to guys that think an extra 20 Lbs and a few inches of height don’t matter. Tell them to add 40 Lbs. to the top of their seat then you’ll be 20 lbs. heavier and more top heavy than me and let race again. Even then you still have more aero drag.
If you want a fun chassis that will last forever go back to 2000 before they started making flimsy frames that get punched out in one season. I hear the big teams change frames every 3-5 races and they straighten them on special jigs at the track.