I have an 01 SSEI L67 that just started knocking, I wanted to know if instead of a complete replacement L67, if I could get a low mileage L36 block to replace mine? Is that the main idea of a "top swap"? Any help would be greatly appreciated. Thanks everyone.

Yes, you can do that but will need to do some tuning on the PCM. You will also have to lower the boost by about 3psi

To lower the boost I would increase the pulley size?

Yep. .3 is about 3 psi

are you planning to mod? or keep it stock?

FWIW, I did exactly what you described with no pcm tuning or lowering boost. I have 4* of knock retard at low rpms and high boost.

I would like to mod as money allowed, first is cai and headers.

What cams would I be looking to buy? The one for the L67 or L36? Since the block is L36 or L67 cause I have all the supercharged workings?

You can use a supercharged cam, a Hot cam or a S1X will work great.

Can I use a 2005 bonne L36 block in a 2001 ssei top swap?