x2.
A 4.3 is a small block Chevy with the back two cylinders cut off. If this is such a bad choice- why do so many people use the bigger brother for a swap-in engine?
Actually it's half of each of the middle cylinders that's cut out.
A 4.3 vortec has at least as much power as many small block v-8s and less weight. The bellhousing adapters all fit, as do the motor mounts. I would absolutely consider a 4.3 swap over a V-8 swap. It's stupid reliable, cheap and available everywhere.
A toyota 3.4 swap is pretty do-able too, but pretty expensive.