what's the difference in these motors

[txhunter69]

today i bought a 1990 4.3 l chevy v 6 and was under the assumption it was a vortec because thats what the man told me come to find out it isnt but i couldnt tell a difference between it and my 94 v6 thay have the same angle on the intake bolts they have the same tbi same every thing i didnt think there would be a difference so i bought it running for $250

bad idea??

[bigblock455]

If I remember this right a standard vortec engine is a z code engine. They also made a W code engine for the years 92-93 which was a performance version the difference was the W code uses a balance shaft, roller cam shaft,different heads and central port injection hope this helps