Can you install a 64 on up small or BB Olds in these cars without a total refab? Are these models a solid frame car?

 

The 61-63 cars are unibody. You can install a later engine, but why? The aluminum 215 weighs 320 lbs soaking wet. An iron Olds motor weighs 650. Do you really want that extra 300 lbs on the front wheels? Not that I'm biased or anything () but I suggest using a Rover 4.6 short block or stroker 215 short block using a 300 crank to build a 260+ HP aluminum motor. Those cars have about a 2,600 lb curb weight, so 260 HP gives you the same power to weight ratio as a W-30. That's an easy number to get from one of those motors. D&D sells bellhousings to adapt a T5 or plates to adapt a BOP transmission.