I put a 454 big-block and a top-loader in a '30 Tudor sedan, and had no overheating or footroom problems with three pedals. My car wasn't channelled, so the flat floor gave a reasonable amount of room. Isn't an A-bone about the same width as a '32?

With a big-block, you need a good radiator and a high-capacity fan with a complete shroud. At least with a stick, the radiator isn't cooling the trans also.

If everything is in good condition, low 20's seems OK, but the Jag rear-end would worry me a bit. 454s can be torque monsters. With decent tires and a heavy foot, you could generate some shrapnel back there.