Dave, Glad to hear the ball joints came out so well, I personally think you will be 100% fine on geometry, even though (the new) Oze has had less than good reviews by you I bet money they don't make there own suspension or crossmember parts, as I haven't seen to many frame manufacturers make their own parts (though there are some like TCI) but the company is in business to sell kits not engineer suspensions and by the fact the use Ride Tech arms tells me its probably bought and welded on. Even though the ball joints look flimsy a Volare weighed way more than what your rod will (which your joints where made for) and the Volare is a much better joint than a stock Mustang II, though your correct there is different quality even among Volare joints.
The only part you might check on is I have only read on mustang II geometry that the lower a arm should be level at ride height as opposed to the upper arms. I have a superide (not superide II) on a rod and it doesn't use any of the same settings as the Mustang II and the lower arms are not set level, I do know when I purchased it I talked with Heidts and their suspensions at the time where all engineered to use alot of stock components to build there suspensions (ex. rack on a Superride was a Omni) the a arms and crossmember where custom though. This was when Gary owned it years ago, when he designed the suspensions. If you want to contact an expert and can't call Oze to find out who manufacturered yours their is one on The Hamb and he goes by ELpolacko, check out his posts the guy is an expert and you could contact him if you are indeed worried, if there is a place to be worried its this area and brakes! I hope everything goes well!