I have a 1999 extended cab shortbed 4x4 with 4.8 and 3.73 gears, I just got back from my first trip with this truck, it did great except for the long rolling hills on the interstate, It was really hard to maintain my 70-75 mph speeds without it downshifting on these hills which i dont like, it was really bad since i had my 700 pound motorcycle in the bed of the truck. My old 1989 silverado with 5.7 TBI never had to downshift going up hills on the interstate and i want to make my 1999 more like that. Would dropping in a 5.3 help much with this? Yes, i already know a 6.0 would but i already have access to a 5.3, so thats why im asking about it. I would like it to not have to work so hard on the next long trip on the interstate hills so was thinking of dropping the 5.3 in if it will actually do better with this...?

 

It may help, but I don't know that the difference would justify the swap. I'm not saying it would be a waste of time, but the 5.3 won't net much more torque stock for stock. If you have the time though, I say go for it buddy. Definitely won't hurt anything lol.