SSBC kit, what spindles?

If you are using a disc brake kit that utilizes the 10 inch drum brake spindle, which it looks like you are, any 10" drum brake spindle from 67-76 will work... They are available everywhere (used) and come up frequently on the for sale section. Or just put in a wanted ad for 10" drum brake spindles, and I'm sure you will get quite a few responses...

For lower ball joints, use the ball joints that are for a 10" drum brake spindle for any 67-76 A-body. You will have to use big ball joint upper control arms, you cannot use the small ball joint units you have now...Once you acquire the large ball joint A-arms, use UBJ from any 73-76 A-body that had disc brakes...

You can find the ball joints cheapest at rock auto...