frame ties

They should have had them from the factory IMHO. Doesn't matter if your car isn't going to be a race car, you'll notice the difference. Fewer squeaks and rattles, doors will fit better, handling will feel more solid.

If you have the bolt in kind already those will be fine. They're not the strongest out there, but they're easy to install and they will still make a big difference compared to not having them. It's better if they're welded in place, the bolts will not hold them as solidly. But you can definitely bolt them in to get them located and keep them in place, and then weld them in once they're located. Then you can take the bolts out and weld up the holes.