58x 4.8, 5.3 ??????

[JJAB]

Guys, I am about to purchase a 2007 Silverado Classic. I am getting a heck of a deal on the truck but the down side is, it has a 4.8 with a lot of miles. For no other good reason, I know I am going to want to go in that motor and replace the crank to magically make it a 5.3. Here's my question, if I find a pre-2007 5.3 crank and rods, can I just take the reluctor ring(s) of of the 2007 4.8 engine and put it on the pre 2007 5.3 crank. This will give me a good reason to rebuild the engine anyways.

Also, it this is successfully done, with the engine cubic inches equating to 5.3, would a tune be necessary of just beneficial?