Hello, I know theres an obscene amount of turbo threads on every diesel site but I've read an reread with no real understanding on my side.

My truck is a 2011 6.7 3500, deleted with 120k miles.

H&S tuner that no longer works (looking at replacements now). I do minimum towing but i constantly carry about 6k on a welding bed.
And I'm in the mountains in NC.

The turbo question is, I read at one point that a 64.5/.90 size or around there would be a good option to replace a 6.7 holset VGT. So I'm looking to order the HTT s300 direct replacement.

I'm not looking to go for a 2nd gen swap at the moment I'm just looking to get it back on the road at the moment.

Then I see s366 turbo set ups and read other numbers like 62 or 63 being good options.

I'm pretty new to diesels but could anyone tell me if the size I'm looking at (64.5/73/.91) is too big or too small? If it's one or the other, is there extremely noticeable problems or differences if i am to go too big or too small to the point of it being a lost investment if I were to make the wrong decision?

Hopefully this makes sense and please let me know if i left anything out. Thank you.