I have access to a new set of 1.6 ratio roller rockers; would they be worth the time to install them?
Likely, anything you can do to make the cam act bigger will help- to a point. It would increase the lift to 0.425", but w/o knowing how close to the limit the springs are w/1.5 rockers, it's hard to say if the swap would work as hoped, or not. I'd be considering a different cam and springs to better match the TC and rear gears.
With your HP peak RPM where it is, the 4500 RPM stall speed isn't going to work- the engine will also be WAY beyond the HP peak going through the lights. Either less gear and TC or more cam, IMO.