6'3 and in need of assistance

[dickenshero]

Hey I recently found this sweater and blazer on my wardrobe that is so cool but I'm unsure of how it fits. I'm a skinny guy 6'3 155-165 lbs and I want to know what size I should buy. I'm going to be gaining major weight during the winter (like 20ish lbs, I'll probably be at 190ish) because I have to bulk up but can anyone tell me if a size large in berberry brit would be the best for me or should I get a size medium??

Also on a side note if anyone knows this shirt or a shirt that looks like this I'd appreciate the knowledge.

 

[Gauss17]

How big are your shoulders? That will dictate it.