Your BF's sizing is similar to mine. I am 6"3" also. Here is where I get mine...www.sheplers.com
Based on his ultimate size, the recommendation would be to add one inch to the waist and four to the length arriving at 35X40. They have them in this size. Be advised though that I wanted to end up with about 36X36 and my 38X40's are a bit too loose for me. If I could do it again I would have went with 36X40 as I believe most of the shrinkage is in the length. Also be advised that recently Levi's has altered the 501 slightly. Yes, they actually do that. Owing to hip-hop influence, the 501 is now a bit baggier. This might explain my results. So keep this in mind when ordering. Good luck.