What is your desired result? What is your application? When you say “I need torque!!” are you pulling a boat? Stumps? Or do you just want to tear up things? More info will get you a better answer.

One way to increase torque is to lengthen the crankshaft stroke (as stated by Denny) and the rod length to the maximum possible. Try and get your compression ratio to 9.5:1 - 9.75:1 with iron heads (use Vortecs). Use a hydraulic roller camshaft specifically ground for high torque and use roller rockers.

Bear in mind that your crankshaft weight plays here too. A forged 350 crank (stock) weighs 50-53 pounds, depending on if the leading and trailing edges have been rounded. 3.750 is going to be 54-55 pounds, 3.875 typically come in at 54 pounds.

If you’re running an LS1 – you can go all the way to 4.250 stroke with a crank that weighs 54 pounds.