I am replacing the radiator on a 2010 pt cruiser. The original radiator does not have transmission cooler, it is separate. But new radiator has trans cooler as part of it. How do i block or bypass those?

First: Obtain the correct radiator. If you insist on using the incorrect one, keep in mind that the transmission cooler is only used for transmission fluid. Coolant does not travel through those cooler lines. Therefore, coolant cannot leak out, unless there is a flaw in the radiator.

ALL aftermarket replacement radiators will have provisions for automatic transmission lines - it is simpler that way for the manufacturers as well as parts suppliers.. Just omit the fluid cooler in the replacement radiator - - as stated - no coolant will leak out.