FWIW, some years back I had a 406" LA, iron heads, T-quad on Eddy dual-plane intake, cheap/small headers, A/T, 3.23s, AC, street Duster.
Went with an Engle FT hydraulic 214/224 @ .050, .470/.504, think it was on 110 CL.
Had perfect street manners, a nice bark & lope, pulled very well, got 17MPG @ 70 MPH.
On an iron-head LA stroker, 9.5 is about max CR on 91 unless you've got a lot of overlap to bleed dynamic CR.