few electrical queries

[steve8274]

hi all
wiring my car at moment but have a few queries. anyone help?
1. my loom only has 2 wires going to master cylinder cap. cap has 3 connections. any ideas which ones i connect too?
2. gearbox reverse switch leads to a plug which has a black/blue, black and a brown wire looped back on itself. loom has a single light green wire for reverse. any ideas?
3. handbrake has 2 wires. does one connect to switch and other just an earth?
4. is it ok to locate megajolt on firewall or next to battery tray in engne compartment?
thanks for help
much appreciated
steve