I would forget the small block in a big car like that. Stroker small blocks can make big power but are expensive (ask me how I know). I would go with a big block. If a 440 is to expensive a 400 can be had cheaply and with some better pistons will make good power/torque. Later on you can add the 440 crank and build a 451 stroker out of it.

If you K member is a small block you can get conversion mounts from Schumaker making this a simple swap.