I have a LS1/LS2 with a cam with 612 lift, I would like these rockers 1.9:1 HIGH RATIO ROLLER ROCKERS 2 SUIT VT-VZ LS1-LS2 but I feel 1.8 ratio might be more suitable, does Mace make 1.8 ratio roller rockers?

Given the lift of your current cam, we would not recommend these rockers. We don't offer an equivalent 1.8:1 ratio rocker at this point in time, however this may change in future. In saying this though, we would still be reluctant using this ratio of rocker with your application, unless you can 100% guarantee that there will be sufficient piston to valve clearance and you use appropriate valve springs for the application.