Yea, this changed in 09 on the GMT900 trucks.

 

That middle one looks like the new sensor. Google ac delco part #213-3949
I posted a link a couple responses ahead. My clamp and rtv solution seems to be working without problems and basically cost nothing to do. I might buy the new sensir later on down the road. What are you doing regarding the vacuum port for the PCV? I put a tight fitting rubber bung in the hole an routed my hose to the nipple on the passenger side. This is temporary, i want to find the new pcv tube that fits.

 

I'm going to resurrect this 10 yr old thread to share a hack for this problem.
I am installing a Holley terminator X on my LS and needed to use the old style MAP sensor or buy a $$ harness adapter. I opted to use a new MAP sensor I had laying around but it's the old style. After looking for a thick O-ring that would adapt it, I found a rubber grommet works great.

If you have the Harbor Freight grommet kit like the one pictured, just use the 3/8 size. It is a rubber grommet with .244" id and 17/32" od. The HF grommet is 16 thousants of an inch larger in dia than the O-ring on the newer style I took off the manifold. It fits snug on the MAP nipple and in the port bore. Shouldn't have any vac leaks. Use some RTV as lube if yours is not as tight a seal-.

Grommet kit from Harbor Freight

Use the 3/8 size grommet size