No they are not the same. The water passages in the head/intake manfold are different too.
So is the respective height of the intake port. Port alignment is not the same.
heads and intakes are not swappable between the GEN I motors and Gen II LT-1 LT4 motors.
A L-31 vortec head needs a vortec intake manifold. There are plenty available so no good reason to consider adapting other stuff.
All the "L-31 Vortec" engines are Gen I