What kind of plugs and wires are you using? You wont see much of a spark if they aren't grounded in the block properly. Having them out of the block and running juice to them may damage the coils. I'd suggest using an ignition tester. As far as the protrusion specs go, I wouldn't be much help on it. I have never taken a chance on using an old tensioner.
Remember to check the fuel system!
Test the ignitor as well. The "gassy smell" you are experiencing is probably due to an ignition issue and not fuel. Again, what kind of plugs and wires are you using?