Another muscadine arbor renovation project

I have a very old muscadine vine that I'm trying to bring back under management (it's on an overhead,  walk-under arbor).  The problem is that there's multiple, really big trunks coming out of the ground, none of which are really "straight" - they're mostly crooked and inter-twining but all do make it to the top where they branch every where!  I've been trimming the top pretty severely over the last couple winters but with so many trunks in place (easily 5-6), the canopy becomes way too thick and the fruit crop suffers, as a result.  Also, to complicate matters, one of the main, central trunks actually immediately branches a couple times right at the soil level.  Do I just need to "pick one" and clip everything else down to soil level and if so, how to choose?  Also, how do you stop the frenzy of new growth at the base when this is done (particularly drives me nuts!)?  Thank you so much for your time and knowledge!

I think you are correct. As you said, "'pick one' and cut everything else down to soil level." Though all the trunks are crooked, pick the straightest. Yes, there will be a "frenzy of new growth at the base." There's nothing to be done about that but to keep removing the sprouts. The easiest and most effective way is to rub them off with your fingers while they are still very small, young and soft. Wear gloves so you don't rub your skin off in the process. Eventually the sprouts will stop emerging.

You might find it very difficult to untangle and remove the mess on the top of the arbor. Try to retain what you need that is growing from the remaining trunk. But if it becomes impossible to do so, consider cutting the main trunk at the top. Then remove all the old growth from the top of the arbor. It should re-sprout. Choose a few of those vines to form arms radiating outward from the top of the trunk. (I'm assuming the trunk is growing under the center of the arbor.) You will probably have little if any fruit the first year or so, but your arbor will be easier to maintain.

You might not want to prune so radically. If not, I understand completely.