mods for a vt 5L on gas???

[vtss5spd]

I have a vt 5L and have already put advanced headers and a dual 2 and a half into 3" tail pipe cat back exhaust on. As i am only 18, my wages arent huge and im getting lpg fitted in a couple of weeks, as everyone knows an ss isnt exactly cheap on fuel.
I just want to know if anyone has any ideas on what would be my next step in the search for more power, i want to be able to make up and exceed the power it has now, after i get the gas.
I also wanted to know if anyone knows where i can get, if it is available a short shifter kit for a vt 5spd, as the throw is to long.
Thanks