Barry,
I checked quickly for rear spring part numbers on my BH27NOB this weekend and didn't readily see any part numbers on them, a closer inspection when they are completely unbolted from rear axle in less than two weeks will net the answer.

They have 4 1/2 leaves on each side - as do the majority of non-Hemi/340 70-71 E Bodys. We must remember there are Stnd duty and also Hvy Duty 4 1/2 leaf springs - a small but definite difference. My BCS has S13 susp & 044 code for rear springs, so I think its safe to include a BH27N and JH27N on the list for 043 springs too.

I did see in the '70-1 Parts catalog that HT 318/383 2bbl gets a different Std duty spring than Conv 318/383. And may have meaning for the 043 springs and there correct application(s).