You can use a 3500 plenum on a 3400 but it is not exactly a direct bolt on. You will need an adapter plate for the throttle body, and to get the most out of it you will want a lx5 throttle body to bolt on to it. The fuel pressure regulator is in the way of bolting on the plenum and will need to be clearanced by notching the regulator bracket and or grinding the plenum neck. Also your coil pack bracket will not bolt up after but there are ways around that!
If you really wanted to the 3500 heads and lower intake will bolt to the block aswell.
2004 Olds Alero 3400 v6 15.32 @ 88.69mph Bone Stock
1999 Olds Alero 2.4 to 3500 swap (running), Ported heads. totaled by a honda
2002 GAGT 3500 swap. parting out
1993 c1500 turbo 3100 swap 5psi.
1976 Cutlass 350 olds stock for now