First of all I would like to welcome to the TDR it's good to see new blood coming on board.
As far as bigger lines go I would say that your existing stock lines will do just fine. You can see my RWHP and Torque numbers in my signature. Those numbers were done on stock injector lines. I have not heard of anyone using larger lines with a VE pumped 1st Gen. Remember a diesel is just like an air pump air in - add fuel - air out the exhaust. I have always felt that a good balance is necessary between air in - fuel added - air out is the key to best performance and RWHP/torque.
You might want to fill out your sig. it will help us to better help you.
Bob