As Thunderchicken said, the GASLIGHT rules are very easy to use and adapt to your own environment. I have played large games with just the standard rules, but the Battles by GASLIGHT supplement allows you to speed up play a lot. The Yahoo GASLIGHT Group is very good for support, as it is moderated by the writers of the rules and they and other group members will reply to any questions you have relating to the rules.
I have created a GASLIGHT playsheet in Word, that can be modified easily to add house rules or new weapons you wan to add to the game. If you decide yto try GASLIGHT drop me a PM and I will send you a copt of the playsheet,