piomen, current US government food health guidelines call for ground pork to be cooked to 160 degrees internal and whole muscle pork to be cooked to 145 degrees. As pork loin is very lean and is tapered in thickness it is easy to dry out so my preference when using a kettle grill is to aim for 145 with fairly low indirect heat. If you put a pan with water in it on one side of the charcoal grate and keep your coals on the other side placing the meat over the pan gives you protection from the direct heat and the water helps keep the air moist while regulating the temperature swings a bit.
Using well soaked wood chips or hunks for smoke will provide smoke with less heat than dry wood will. Placing the lid vents opposite the coals and over the meat will ensure that the smoke has to pass over the meat to get out. If you use wet wood part of the smoke you see will be steam until the wood dries so don't worry if you see what looks like heavy smoke.
Another trick you can use to lower the chances of drying a boneless loin is to cut it in half crosswise, rotate one half and tie it into a larger thicker roast. That will make a single piece of more uniform thickness from end to end and which is about as thick as it is wide. It will help it to cook more evenly than a whole loin with it's varied thicknesses (although maybe at the cost of somewhat less smoke flavor....). If you do this my experience is that if you are going to use a rub apply it after tying the roast as any rub in between the halves gets pasty and remains raw.
You'll find that keeping some basic notes regarding seasonings and cooking techniques will really aid in remembering what you've done. Without notes it can be tough to keep doing what went well or doing better next time with those things you want to improve.
Good luck and let us know how things go.