extending my track

[sbsho]

so im lookin to get rail extensions for my 96 proaction skid to make it a 136 or 141-144. extendin it to 136 i dont have to change my gearing correct? but if i go to a 141 or 144 i do?

i plan on heavily modding this sled to get the best ride and power i can get from it. any thoughts on what else i can do would be greatly appriciated. thanks
-ryan