1. long tubes rob a small amount of low end torque and gain around 30rwhp peak.....
2. shorties do not flow better at high speeds (rpms)....shorties arent much better than manifolds......
3. if you want more low end torque with a stock lt1, a torque converter will solve your prolem a PI 2800 will work perfect with a set of 3.73s. you will have more low end torque than street tires can handle you will need drag radials to hook.
jesse

 

As others have said, gears and converter rather than engine mods seem like the best bet. Headers will help. As Mike stated, long tubes tend to improve low end and mid-range torque better than shorter headers.

Rich Krause