Nice rig for the money and with some minor repairs and upgrades you will have a great truck for a relatively small investment. A factory automatic transmission cross member will work or you can buy a generic automatic tranny cross member from many of the aftermarket truck parts suppliers like:
www.lmctruck.com
www.classicparts.com
www.truckandcarshop.com
www.oldchevytrucks.com
www.classicperformance.com
I see the factory auto tranny cross members on eBay from time to time. I have a factory auto tranny cross member, that has been chromed, if you are interested.
The mirrors are aftermarket and available at Walmart, K-Mart and most auto parts stores.
Nice truck and please keep us posted with your progress. Congratulations on your purchase and good luck during the process.