I talked to an old racer once about building flow restricted engines. His philosophy was to maximize pumping action of the engine to draw as much as possible through the restriction.
In that vein, getting the piston to dwell at the bottom and maximizing bore/stroke would seem to help.
From the outside it looks like someone could install large sleeves in a flathead block and run as much as a 3.75" bore or so. This requires moving some head bolts and water passages. They were doing things like this quite a while back as I'm sure some of you already know.
http://351c.net/wiki/Magazine%20Arti...zingblocks.pdf
I'm coming from the position of 1/4 mile performance.
What do we run into stroke wise? Camshaft clearance?