3rd party gearboxs and gear ratios.

[SMEGHEAD]

Hi

I currently have a high end AEG, the internals are as follows
Guarder Reinforced V2 Gearbox (one sheared bolt)
Guarder Piston Head alloy
Full Metal toothed piston King Arms
Guarder Advanced Cylinder
Guarder Advanced Cylinder Head
Modify High Torque Gears
Modify Tappet Plate
Modify Anti-Reverse Latch
APS RAF trigger
Random Air Nozzle
BTC spectre mk2
ASG CNC 18,000 Super high torque motor

I am looking to replace the gearbox shell, not really sure where is best shop to look, or if anyone has recommendations, its mainly to make reassembling the gearbox easier.
suggests are much appreciated and whether or not you think they are worth buying.

I am also looking at swapping out the gears for a high speed set, I don't really care about having anything more than 20> RPS, I simply was trigger response, if RPS increase is a bi product of that its fine buts its not a priority, I run an m100 spring, so my question is what ratio would be best and any brand recommendations.

Thanks very much in advance for your time and advice.