i am quite sure it will be impossible to provide full power requirements to the MF STAR (not to mention cooling) onboard the Talwar class.
In addition, MF STAR is a heavy sob - and i am not sure the lighter Talwar's CG will be fine with such top heaviness.
Shivaliks, given their broader beam and better seakeeping can handle it - maybe.
Perhaps its a smaller derivative, and we are getting worked up - lets see
Current radar used by both of this ships are Fregat M2eM which weighs 2.5 tons , and the doc mentions "RA"(guess that means rotary array , unless they want to mess with the mast ) which implies to EL/M-2258 which is rotary(compatible with MRSAM and is AESA) and only weighs 1.7 tons. but they might need to do major changes in the CMS of these ships.
For power consumption both ships have enough juice to power this radar( AESA more efficient and is just a single sided array)
As for the mast it might require minimal changes to incorporate this one.
In the current state both ships are severely ill prepared for air based threats due to arm launcher, which has short-medium range missile, incorporation of MRSAM if possible must be a important part of their MLU.(also they could do networked warfare if their CMS gets a good upgrade).