On a 2.5L engine the largest gains would come from up sizing the tiny exhaust valves.
Very little gains would be realized between the 32mm and 35mm intake valves.
On top of that.
If you are going through all the work of pulling the engine and disassembling it then why not go to a 3L anyway. You could do a full 3L swap for almost the same price as a set of ported heads with 3L valves...