Let's start things off

Gen2 L61 engine (2008 Cobalt LS)
M62 with 3"

Can I swap my l61 head to an LE5 block?

I have a 2006 LE5 block from a solstice w/o oil cooler

 

Pretty sure you can. Are you putting the LE5 in your L61 Cobalt?

 

Correct
I want to use the LE5 block,and L61 head in my L61 cobALT

 

LE5 bare block but use your L61 internals (except for the bigger pistons you need)? I just about done with a Frankenstein build with an L61 head and an LSJ block. I used all 2.2 internals. Only considerations I have had to make changes for was I had to us LNF piston oilers for clearance and I have to install an oil cooler as the LSJ block has provisions for it.

I think you can definitely do it just need to identify any differences beforehand unlike me discovering the LSJ block has oil cooler openings which I discovered when I went to first start it up after rebuild and oil everywhere. If I would have researched more ahead of time I could have easily had that issue addressed when the engine was outside of the car with everything very accessible.