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

Welcome and nice starter ride!

Did the seller/previous owner have the car a while and make all those modifications? Seems odd that he would indicate the block is a 273 instead of a 318? Maybe the seller bought the car with those modifications already and flipped it?
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.