'65 Barracuda 318 LA Transmission Questions

65 is the wrong chassis to learn transplants and big power engines. Really, it is so restricted on headers and space that keeping the stock auto and maybe getting a higher numeric rear and a higher RPM cam profile would get you into the fun zone with a minimal learning curve. 273/4 or even a cheaper 67 318 can rev hard with a 4bbl intake and dual exhaust. If you like to shift, go full manual valve body. Sticks require a manual hump, Z-bar stud, 3-pedal setup and you should address the rather weak 7.25 rear for a stick application. It can be done manually but an auto is so much easier. 360 is the same size as a 273 dimensionally and the bigger 340 logs will fit manual steering just fine. Headers are out there but are >$800.