TDB - i've never smoked beef tenderloin, but i have smoked deer tenderloins. if anyone with more experience in this has any advice, it would be worth listening to.
one thing i can say for sure is that you want to keep these lean cuts moist. a good way to do this is to wrap with bacon. or, you can baste them often with an oil-based mop or sauce. in an effort to keep it siple, some folks just brush with a little olive oil now and then. as far as seasonings go, keep it simple for best results: kosher or sea salt, cracked pepper, maybe a little granulated garlic and/or onion. shouldn't need much more than that.
i'm just guessing about this part, but if it were me, i'd pull them off the heat at 140-150 degrees. if food safety is a top priority for you, i would say that you want to take them to around 155 degrees internal temperature, and then let them rest and coast up to 160 at the most. any warmer than that, and you risk drying them out.
that's the advice i would give for these cuts, as they are so lean and normally would be more suited to grilling rather than barbecue. having said that, the above method should work well.