273 to 340 swap ?'s

Thanks for the responses! I ended up not buying the engine, it turned out to be a 318! Someone had ground off the 318 casting # off the side of the block. Couldnt tell what it was. It had J heads on it, with the internally balanced crank balancer. Upon closer inspection, after scraping off the paint @ drivers side front of block, the I.D. for a 318 was revealed. So no deal was done. Again thanks for all who responeded. I will keep these responses in mind for future reference.