3/4-ton drop spindles for '70

[70Longhorn]

Here's my dilemma. My old C-20 Longhorn is long and low, but it's currently on chopped coils and fewer leafs. I know I could make it work, but I just don't like it. The goal is to keep it it's current height (about a 3/6 drop) but use correct parts. The kicker, it's going to remain 3/4 ton.

It currently has an '88 (R, not C) front suspension (arms, spindles, brakes, steering) and what I want is drop spindles and airbags. The rear will be a notched frame, some kind of link suspension, and bags but that's for another thread.

I have not found 3/4-ton drop spindles for either the '70 or the '88 front end unless you count duallies. In fact, the only 3/4-ton non-dual spindles I can find are for '90+ trucks.

That's the background. Here are the questions:
Will '88 dually spindles work with single hubs?
What about mounting 3/4-ton hubs to 1/2-ton spindles?
Can I convert to '90+ spindles by swapping balljoints, or will there be more to it? (hubs, brakes, ... arms?)
Finally, has anyone seen drop spindles for a '70 C-20?

Thanks for the help!