[67-ls1]

I’ve had zero luck finding a BSFC map for my engine. It’s pretty small displacement, for the car anyway, and not particularly torque-y (sic). I find that when cruising on the highway between 55-65 it constantly wants to drop a gear to keep the same speed. Super annoying.
So I thought maybe I’m in a bad spot torque-wise on the curve???
FWIW, I have 26.6” tall tires, 3.07 rearend gears and the top two trans gears are 0.85 od and 0.67 od.
It’s pretty dam efficient for what it is when I drive it like there an egg under my foot but if I drive it normal it shifts around a LOT. This can’t be good for efficiency.
I’m thinking maybe a lower rearend ratio (higher numerically) might get me closer to a sweet spot. How can I run a test to verify prior to changing?