You think a 16g is going to grip better than a 20g??
Faster spool = less grip.
Also you need a clutch if youre manual... that kid aluded to a 13g which would mean auto, but I assume he was just guessing.
If youre going to go 16, a supra smic will be plenty, but like I said... he wont be happy with a 16g. There is a columbusdsmr with the exact set up + 16g and 550s, he runs mid 13s. If thats all he's looking for than go for it.
You also need an EGT gauge, and a data logger. DSMs are all about tuning. AND, you wont get far with out some porting of your stock gear... exhaust mani 02 housing dot dot dot.
Besides that, a fuel pump and SAFC are manditory to play this game. DSMLink can consolidate the datalogger and SAFC into a cost effective engine management unit if youve got the scrill.
Plan on spending at LEAST 2x what you do in mods to repair what you break and to replace the crankwalked block with a 1g.
The end.