sure could
and there is a tool than NHRA and others use
easier on a SBM than a BBM due to plug location, just roll the car over on its side
If you know the year of your 340 and if the motor has not been rebuilt you can figure it out pretty close- cc of the heads are known (and don't use the blueprint mimimums use the "as cast" J or X or most any 360 heads are about the same
If rebuilt, if you did not do it, you do not know what pistons are really in it
do a compression test- if high figure high compression pistons- if low figure the late pistons
do the math you will be close