Good idea I just finished a mild a12 myself... It's lot of funneith great torque!!! I would most definitely recommend it for a daily!!!
First I would recommend putting an h89 hea on which is a higher comp than the stocker a12, it also oval ports so you can put twin side draft manifolds on....
I had my flywheel machined And lightened well it's lighter lol. I also out a Bice as of flat tops in and from memory it's bored 20 odd thou but I'm not sure.
Next is what sort or carb/s do you wanna run? You can run DHLA/DCOE, solexs, bike carbs EFI or even su's it's whatever tickles ur fancy and whatever you can afford haha.
I would also recommend getting everything balanced, rods, pistons, crank etc. I had a cam reground by wade cams. It has smooth fast idle and picks up at around the 2500 mark.
Then you cam look at head work... Double valve springs, porting, valves etc.
And when you say "gear" are u talking brands or just which way to gonkn building it? Lol I think i shouldnof starte with this question. Oh well.