Your kidding right the only thing that can fit in late sixtes 65-66 are 289's you might be able to pigion toe a 302 in but that's all your getting.Now 67-68 had 390's that might suit your wife it's got nice power and pretty good gas milage. My personal fav from my sn would be a 351C H/O or CJ those are some hard finds but the 2 barrel verson should be easy to find. Why wizard makes a 351 block that makes 425 horse.....I think it's like 4000 dollars but hey it's up to you.