Will Series III fit in a 96?

Is it possible to replace the Series II engine and S/C with a Series III unit or are they totally incompatible?

you can replace the L67 with the L32 in the riviera. it has been done but not worth it unless your engine is blown and you need to replace it. its not a direct bolt up but it will work and requires a new pcm. the only difference between the l67 and new l32 is 20hp (260 vs 240...the same torque IIRC) and i dont know how they got that b/c it has the same bore,stroke,m90,...everything(they changed a few small things like the throttle body, water pump, etc. to make it more efficient. they both mount up to the same tray too. you can get plenty of power out of your L67 with the right mods and its cheaper than paying 4K for a L32 crate engine.

you can get 15 of those 20 hp by removing the restrictor pipe behind the cat. converter and replacing it w/ a straight pipe.. no need to go thru all that work and expense