1.65 adjustable rocker arms

That's about their only benefit. Getting the ratio either corrected or added to......which "could" add a little. Still a pile to pay. I would talk to Gary at RAU first. He can modify Buick straight 8 rockers to be accurate. That may be what I do with this engine on the stand.
Did You see this post on .org?
Clifford Rocker Arms - Slant Six Forum