Hello from NY

Hello all, new to the site and absolutely love it. I have my eyes on a a 66 Barracuda and waiting till the weekend to pull the trigger. I have a few questions for the members here. The car has a 273 w/AT, what's the largest engine what will fit in that year car without any fabrication or modifications? Secondly, I can't seem to find a lot of info on the 64-67 Cuda's and was wondering if these years weren't as popular.

Thanks
Steve