Porting J heads ?

Do you have to run OE castings?

Decide how much power you need to make, then figure out how much porting that would require if using OE heads.
If it’s a substantial amount of porting, and you’re not experienced at it, I’d look at an alternative solution.

Basically, if you’re new to it, I’d try and limit the work to a “good” bowl blend, and live with the results....... or pay someone to do it.
High effort porting jobs from novices often don’t end well.

If you don’t “need” to run stock heads, but want to make some power...... you’d be better off in the long run getting aftermarket heads.