The So-Cal Speedshop bellytank!
One of the most well-known and successfull bellytank racers was Alex Xydias, the owner of the So-Cal Speed Shop. The So-Cal Special was basically a 315 gallon wing tank off of a P-38 Lightning with custom built framerails, powered by a 156 cubic inch flathead V-8. At Bonneville in 1951, the So-Cal team set a new record for their class, running a 145.395 mph average.
The So-Cal Speed Shop team took the car back to their motel and, right then and there in the parking lot, swapped the engine out. They put in a larger, 259 cubic inch Mercury flathead and ran the car again in a larger engine class. They set a record in that class as well, running 181.085 mph.
The team then swapped the engine out once again, this time putting in a 296 cubic inch Mercury engine. It ran a one-way time of 198.340 mph, with a two-way time of 195.77 mph. This speed was a record for its class, until it was upstaged the next day by the Mal Hoopster lakester, which was running with a Chrysler hemi and turned a 197.88 mph average. But the So-Cal Special's 198.340 mph run is still the fastest one-way speed that a non-blown flathead V8 has ever run.
To put all of these achievements into perspective, consider that at 1952's Indy 500, Troy Ruttman (with all of his sponsors and his overhead cam engine) won the Indy 500 with an average speed of "only" 128.922. Xydias was going faster than Ruttman in a salvage yard belly tank powered by a pre-W.W. II flathead Ford and no sponsors.