Which size Serpentine Belt?

Hi,

which size I should choose if I buy an new Serpentine Belt?

1991 Buick Park Avenue L27 Series 1 3800L V6?

On Rockauto I found 2 Size:

13/16" x 86 3/8"

or

13/16" x 103"

Good question. I have the same model as you and have been wondering which parts to get. My guess would be the 13/16" x 103" since it is a really long belt.

I also want to replace the tensioner pulley but they list several models for that as well.

Part No. 1025K6 or GATES Part # K061025 The shorter one would be for the supercharger, if you had one.

Thx, no I have the regular engine L27...

Its a cruiser:D

I also want to replace they pulley.
On rockauto they list 2 sizes, 76x17x25mm and 82x17x25mm. I take it the 82mm is for the base model. However I want to get the Gates pulley, which is not listed at this size as a tensioner pulley, only as the idler pulley (which I don't have)....
Are they the same or is Dayco a better brand?

Dayco is fine brand I think, I bought since 4 Years for diffrent cars the serpentine belt / Idler Pulley and all is fine.
The Idler Pulley are the same size so its the same which one u took... There are just on different about 1mm so its not important.