i have a 1999 lumina and i was thinking or wanting to look at replacing the motor tho i am stumped at to where to look at or how to find what size of motor to get any help would be awesome thank you in advance

 

You have 1 of two engines. You either have the 3100 V6 or the 3800 V6. The 3100 has an aluminum upper intake manifold with 3100 SFI on it. The 3800 has a plastic engine cover that says 3800 Series II. If there is no engine cover then look at the upper intake manifold. The 3800 has a black plastic intake manifold.

 

Or 3400

 

No.... the 3400 was never put into the lumina, especially not the 99.