As with all questions, it depends on your goals, your budget, and your tastes.

I was doing a build on a shoestring budget and the extra cubes of the 460 provided what amounted to free horsepower for the little bit of money I could spend. BUT, I was starting with an empty engine bay. I had to buy everything - engine, transmission, mounts, drive shaft, and more. It sounds like you are starting with a running car. If so, that tips the cost scales to the Cleveland. It is almost always cheapest to build what you have.

You don't say if this is for a street-only car or if it is going to the strip. Either engine could do anything you might want, but the decision depends on defining your goals and planning two builds to compare.

You also don't say what year your car is. '72 & up Torinos are very heavy. For me, this tips the scale toward the big block.

Have fun!

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'73 Gran Torino Sport - 466ci, Performer Intake & Carb, Comp 268H