Crossed over from '67-'72 land and have a question about a manual to auto swap

[DA68]

This Spring I sold my '68 project and within two weeks, stole this great little 65 for $1,800, complete with roof lights and gun rack! It's an older restoration with a few patches, but it had new brakes, tires, a 3:73 posi and rebuilt 400 SBC. Since then, I've bagged the rear, straightened out some wiring issues and just have had fun with it. I need to finish the patina job, disc brake and bag the front, white wall the tires and replace the 3 speed, 'cause I've got some noise coming from it.
Being new to the '60 - '66 world and knowing the manual crossmember is much different than the auto member, my question is can I use/modify a '67 - '72 auto member or is there a better route. Finding the right year auto member, might be tough. Any help is greatly appreciated.