If warranty is not a consideration for you(I don't know the mileage of your truck) you may want to consider the Series 2000 75W-90 for your 5-speed. There are a number of proponents of this lube in the 5-speed. Even though it is GL-5 rated it has given excellent results. TDR member Sled Puller is probably the most vocal advocate of this lube in this application. You may want to seek out his opinions.
Transfer case; I use the Series 2000 75W-90 gear lube. I realize it is supposed to take ATF, but I am interested in the long case life that I believe the gear lube will provide. The Amsoil ATF will work well for you if that is your choice.
I have enjoyed the 275 injectors. Do I wish I had gone bigger? I don't really have any experience with larger injectors, but I am considering trying them. The 275's have given me excellent fuel economy and towing performance with livable exhaust gas temps. If you install 275's AND a hot performance module like the Edge Comp, you WILL need a beefier clutch.