the beef shoulder is the Chuck. Roast can be pulled, but there are 7 different chuck roast, look for one with extra fat and that is the one you can pull. I have done three chucks so far. One pulled great, one only partial pulled and one didn't pull at all.
Not sure what the circumstances are but if one butt is not big enough you might want to just consider multiple butts and then not have to worry about the beef. IMHO, pulled pork is mighty hard to beat and the results are fairly predictable. I had a big crowd over during New Years and I did four butts. The wife helped me with the sides and everything really turned out great. My neighbors are still talking about the Q (I used Florida Jeff's finishing sauce). As a matter of fact, I may have created a convert. One neighbor keeps asking me about the smoker, types of meat etc. I think he may take the plunge. Whatever you decide, I wish you luck.
I could, I have just always been wary of smoking a smallish piece of meat. I much prefer a larger cut (5# or more) Seems to be more forgiving. BTW, do you have a link to the recipe for Florida Jeff's finishing sauce?
I didn't mean to get ya all excited.....but i know how ya feel!!
Alway's go by temp to get ya close, but with some experience you will be able to go by "feel"
When you stick a probe in and it feel's like soft butter.....it's done, may be 10* higher than you planned, may even be lower, but you'll get the hang of it!!
Sorry to give you more thing's to worry about, use what ya know and go from there, it's ALL good!!