I have considered rebuilding my current short block, which is a 283, but recently I have considered buying an assembled short block like the GM Performance Parts ZZ4 or the ZZ383. I am looking for opinions on these assembled short blocks such as are the bearing clearances within spec and is the hardware torqued properly? Are the blocks old or new 350 blocks? Are there any other recommended sellers? I only plan to cruise the car and not take it over 5000 rpms. Thanks.