That's really really good if it's a 59deg block.

The worst case I've seen with aftermarket rockers was on some TA heads that had HS rockers on them. The rocker stands had been milled off, and they had the blocks around the shafts, along with the offset shafts(iirc) like W2 heads.
Going off memory, they were about 1.46 on the exhaust, 1.45 on the offset rocker intakes...... With checking springs.
With 500lbs open spring pressure they were down around 1.43-1.44.

On the BB ones I've checked, using rockers with the std offset, both Crane and HS seem to have about .5 added ratio built in when checking with soft springs(depending on exactly where you have the adjuster set).
The HS seem so have less deflection and are usually still higher than the advertised ratio even with 600lbs+ open pressure.
I had a set of HS 1.6's on some SR heads...... Checked about 1.67 with soft springs, were still 1.62-1.63 with 700lbs open pressure.