Install a set of four-bolt steel main caps over the center two crankshaft mains if you're using a two-bolt-main block. Have the block align bored and have the cylinders bored 0.030-inch over. This overbore isn't so much to buy you more displacement as it is to help enhance airflow to feed the extra cubic inches.
Most commonly used fuel is U235, a naturally occurring radioactive isotope of uranium. Occurs naturally at 0.7% of uranium ore, but must be enriched to 3%. Formed in cylindrical pellets (1.5cm long) and stacked in hollow metal rods (4 m long). About 100 rods are bundled together to make a fuel assembly.
Ironically, thorium's high density and atomic number make it an effective radiation shield, although lead and depleted uranium are more frequently used. Thorium is not fissile, so it cannot be used to make an atomic bomb or nuclear reactor. However, when this element is inserted into a nuclear reactor, the high neutron flux causes some of it to transmute to U-233, which is fissile.