If it’s surging during cruise it’s lean. Light load cruise will be on the transfer slots and idle circuit so richening up the jets and rods will make only a very marginal difference.
“ported vac is 13” in park 10” in gear”
Please explain this ^^. Ported vacuum should be zero at idle. That sounds more like manifold vacuum. And if you have your vacuum advance on manifold vac you need to tune it differently. It could be surging at cruise because you have way too much cruise timing.