Neither, I would go with 3400 Turbo
Personally I'd go with the 3100. Less work involved in the swap.
On another note good luck trying to get a straight answer from most people on it. I posted a similiar question about two engines, a 3100 and a 3.1; here and on V6 and everyone chimed in about a different engine. Everything from a 3400 to a turbo 3.1 to a Nissan motor.
3800 will give you more power overall but harder to do the swap id do the 3100 theirs more you can do to it easy and you can also swap out the top for 3400 and gain even more power from that....
or you could always ggive me the 3100 lol
i'd deff go w/ the 3100. because 3.1 came in j-body's and it just seems like the logical answer. it will be easier to work w, and everything will just fit together better. it's hard to explain but i'm sure u understand what i'm trying to stay. it's almost like it's stock fast but it ain't stock
People say that what doesn't kill you in this life
will make you stronger. I'm not sure if that is true
or not, but i do know one thing-You have to learn from
it and it has to make you better.......it has to.......
3100 2000- and 3400 intake manifolds are the same, same as the heads. but thats only the 2000- 3100 engines