can i use the drive shaft from the 12a for a 13bturbo swap on my first gen or do i need one custom made if so does any one know were to get one and do i need custom brackets for the tranny too

 

You need to get a custom driveshaft made. Read this page and click o the TII swap link https://www.rx7club.com/1st-gen-archive-71/1st-gen-rx-7-faq-page-507782/

 

If you are keeping the 1st gen tranny and using the SE engine mount, you shouldn't have to make any changes. If you are using the TII tranny you will need the driveshaft that came with it and have it modified. Most decent sized towns have a driveshaft shop that can modify your's to the correct length. You will need the TII yoke and the original rear flange from you car for parts.