Pipe dream motor swap: What would you bolt into your A-Body?

Just to avoid crazy responses like a "3000 horsepower R-2800-8 Wasp engine" from a P-47 Thunderbolt har har har" or something out of a top fuel dragster, let's limit the discussion to engines that would:

A) actually fit (possibly with some significant fabrication)
B) actually work in the car for how you drive it or how you would like to drive it in the future.

PS: specified "motor" since electric propulsion (which aren't "engines") shouldn't be left off of the table here.

Go!