986 2.7l block with 2.5l head
 

Are there any one doing this is it possible?

You can but the compression ratio will be different. Plus the intake ports are different.

And of course that 2.7 would have to be a 5 chain to pull it off… There are 3 chain 2.7s abound.

And how putting 2.7l crank in 2.5l block

Lots of them running around here on SoCal tracks.

yes, 2.7/3.2 crank into a 2.5 block with 2.7 pistons

but.. the 2.7 heads/intake is leaps/bounds better than the 2.5 stuff.

It works well :)

Several cheater BoxsterSpec cars here in SoCal ran 2.7 bottom ends with 2.5 heads/intake.