Assuming you have already figured out how set up an area on your grill for indirect heat (if you can, it's easier with a charcoal kettle grill),
and can get a consistent known temp from your grill (check your grill's thermometer),
I would use a
smoke tube.
If your burners run lengthwise front to back, setting a spot for indirect heat (e.g. only the left hand burner on) will probably mean cutting your racks in half,
if they run lengthwise side to side, then you can just run the front burner and have the back space open for racks.
Note also you can get a vertical
rib rack to make the most out of your space
(I started way back in the day on a round charbroil gas grill, maybe 18" across- I used to coil my racks and hold them together with skewers- worked pretty well!)
Convention has you using wood chips in a foil pouch or smoker box,
but the smoke tube is what I use to supplement on my smoker, and it works well.
You can pick up pellets at Lowes or Homies, and you should get 4-5 hours out of a full tube of pellets.
If you plan on doing a longer smoke, get a couple of tubes to easily swap them out when one is burned out.
Only thing to note is you need an open direct flame to get the pellets going I use the side burner on my gas grill for this.
Anyway, some good points on
this thread, I'm sure there's many others.
As to the particulars of my last batch,
it was done on a Traeger pellet smoker-
Racks were about identical in size (2.8 lbs pre trim)
I smoked at 225* for 4-4.5 hours, checked for near doneness (snap test, not temp or tear test),
and then basted with bbq sauce (honey added) and did another hour at 250* to set the sauce and bark
Shout out if you have other questions- lots of experience in this group.
