what motors are interchangeable with 95 Buick Riviera evight vin is k

The 95-99 Riviera all used the 3800 V6 engine.....there was the standard non- supercharged engine and the supercharged option. I would stick with the 95-99 years which gives you lots of options as the same engine was used on other Buicks, Olds, Pontiac. All the makes had a standard 3800 and the supercharged option. One common supercharged version was the Park Avenue Ultra....all Ultras came with the supercharger. All of the engines should be an easy replacement for your car.

Thanks