http://www.rceng.com/

they have conversion formulas.

just look for em

Here's the equation that I find to be the most accurate:
[(lbs./hr) x 60] / 6.177 = cc/min

A 55 lb/hr injector is roughly equivalent to a 535 cc/min injector.
This is, of course, not an exact equation, but it is very accurate.

To get an exact cross, you would need to factor in the specific gravity of your fuel, since you're converting a volume per time to a weight per time, and weight is a function of gravity.