i have a lo3 and im doing the l31 tbi swap. I seen the block at gmpp for like 2200 but im kinda on a budget. So i went to autozones website and they had 3 dif brands of replacement longblocks ranging from 1300 to i think 1700 and one brand even said it has 20 more hp and 10 more tq then stock which would make it 275hp (same as lt1). Have anyone bought a long block from autozone or advance auto parts? would they have the same power levels as gmpp stock l31?

 

don't forget the core charge on those. might be the same as a new GM motor.