The papers were with the cutout. The documentation is all of two pages, a warranty page and the instructions, but the instructions have important details on them so I guess that's not bad.

I went and did a search on ls1tech, the stock piping should be 2.5" before the y and 2.75 after. It seems like most people go with dual 2.5" cutouts, I think a 3" would work coming off the single 2.75.

That's a good question for GM Tech- would a single cutout off the 2.75 right after the y be advantageous? Is it worth it for 98SOM to buy the single 3" and have it welded in with some sort of 2.5-3" Y pipe?