I definitely wouldn’t get one done at a convention. You should look around at the shops in your area and talk with the artists and get input on the work you want to get done.
7mm-08 would be my choice but you are really not going to notice a difference between the two. Plus if you keep the 7mm-08 you will be saving money by not having to pay to get your 308 chopped down.
I have been using iron will 125s and g5 dead meats for the past 5 seasons, but I only have a few of the dead meats left so I will probably try something new next season.