While not a true build like the others in this post. I did "build" the Seiko 300m Tuna that I wanted. It seemed that every generation of Tuna added something but also took something away. In this case, they finally offered a Seiko 300m Tuna with a sapphire crystal and brought back the round lume plots and old style Tuna hands in the current series (SBBN043/045/047) but kept the day/date wheel with a black background of the previous generation instead of bringing back a day/date wheel with a white background. I have always liked the white background day/date wheel gave a nice contrast with the black dial. I love the look of the SBBN007 with its "crop circle" lume plots, the no X or Marine Master dial (just professional 300m) and the white day/date wheel. What I did not like was that the SBBN007's case only had drilled lugs on one side and not the other. (I use a longer shoulder-less spring bar that gives a better fit then the seiko OEM bars but I need all the lugs to be drilled in order to use them.)
I also like having a black bezel insert.
Now I don't have the talent and all the tools a lot of the other watch builder/modders have so I was not going to attempt to screw with replacing crystals and gaskets and bezel inserts(I tried my luck with a couple of bezel inserts years gone by and failed badly)
Now what I did have was a well beat up SBBN007 and a cheap SBBN045 so i simply used the SBBN045's complete case (with crystal, bezel. chapter ring, case back and crown) with the SBBN007's complete movement (the movement was installed with no issues) and took the SBBN045's complete movement and installed it into the SBBN007 case to use as a beater watch/future source of parts watch.
I now have the Tuna I wanted with everything OEM Seiko parts. The SBBN045's sapphire crystal improves the look of the watch