The rear lower shock mount cracking is a pretty common problem for yj’s. Mine bit the dust after some light wheeling last weekend. It took me a while to find a good replacement part. Posting a link here to the replacement bracket I ordered. It is made in the USA and looks like an upgrade. Here is the link:
www.summitracing.com

M.O.R.E. 98200 M.O.R.E. Shock Mounts | Summit Racing
Free Shipping - M.O.R.E. Shock Mounts with qualifying orders of $109. Shop Shock Mounts at Summit Racing.