Since I have failed to communicate some of my posts clearly, I do not want any confusion. Forgive me if I am talking below your level, I just don’t want a mistake and I feel this needs to be said.
In order to grind the ports in the heads, the heads need to be removed from the engine and fully disassembled. Then, they need to be thoroughly cleaned before reassembly. Any metal particles and/or grinding dust will destroy and an engine.
If your long block is already assembled, I would just put it together. Realistically at your horsepower level, you will not notice any difference by just port matching.
Regards,
Joe