Couple of ways to go here. The stock 5-speed will bolt up to the block, but it may not live long behind the 5.3. You may need to get a spacer to get the proper insertion into the disc. What Scary said above about the flywheel-its been done a lot. Another way to go is to use the T-56. Plenty strong and the first 4 gears are tightly spaced for performance and two over drives for economy-best of both worlds. It bolts up with out a spacer needed (if you get the LS version), and should use the same driveshaft. There are a few write ups about this swap too.