66 Cuda suspension question

So Im sitting here, freezing my tail off, and browsing my new jegs catalog. And my question(s) are this
I see in the Jegs catalog there are two different size torque bars for this car, a .890 and a .920. Both are MOPAR performance parts. Whats the advantage/disadvantages to these?
Also Im seeing MOPAR super stock competition rear leaf springs , and XHD OEM leaf springs. the mopars are lower price but whats the difference
Also preferred shock brand/model?
Just building my build sheet for my project to get an idea of prices.