is there any difference in the crank shaft between a 2.8 and a 3.1?
is it a different stroke?
if there is a difference between the stroke could i make my 2.8 a stroker?

The only difference between a 3.1 and 2.8 is the stroke.

3.0 inch vs 3.3

As far as I am aware that is basically the only difference between the 3.1 and 2.8

Difference is in the crank btw, they have the same length rods, its actually somewhat common to stroke out 2.8s by putting in 3.1 cranks, but I think you have to swap the pistons over too or else you will have interference issues if memory serves. There are other minute details where they differ, but as far as major components go, ie. heads, blocks, intakes, valvetrain, rotating assembly, its all interchangeable for the most part.

Yeah you could, and while your tearing into the engine you could upgrade your rockers and pushrods, and put a cam in there too!

since there is a difference in strokes would the pistons clear the heads and valves

I am fairly sure you need to use 3.1 pistons if you use the 3.1 crank, 2.8 pistons might interfere, I may be wrong though.

Uhg...

This is so simple and discussed to death...

To change a 2.8 to a 3.1, the parts that need to change are the crank and pistons.

Well there you have it, that confirms it, he knows more about specifics than I, that or he just has better memory :P