That's going to be a fun truck when your done. Don't worry about others opinions, its your truck, do what you want with it. Over the years you may learn their right or they might be wrong.
I would get all the brackets for the newer serpentine system so your alternator and AC pump trade places, but then you will need new pump and AC lines.
When I first put my 454 in my suburban it would detonate when towing, I retarded the timing a little bit and it got worse, so I advanced it and so far its seems to like 8 deg adv