My 273 turned out to be a 318...what did I buy?

The seller is into B body mopars. He brings mopars back east from the west. This valiant was from California and he drive it for about 2 years. According to him, he installed the fuel pump to correct a stalling issue. I'll definitely look into the inertia switch. He wasn't sure what had been done to the engine but said it was a former drag car. He also installed an 8 3/4 3.23 sure grip rear. Surprised he didn't know it was a 318 either. Sent him a text when I saw the casting numbers....haven't heard back yet.
If a drag car it is likely .030 over with KB167 pistons. Same 10.5:1 compression as the 273 Commando and 50 more cubes. At approx. 2750 lbs definitely not a slouch!