A couple of notes on the 273 to 318 or 340 swap....first, if it's going in a manual trans car, look to see if the crank has been machined for a pilot bushing before ordering the bushing. Most automatic cranks didn't get that final machine work done, so, you need to get an aftermarket pilot BEARING to install in the converter register, or machine the crank for the bushing. The '64-7 273 crank has a smaller diameter register than the 318/340/360, so, the Magnum bearing won't fit. Same problem with using an automatic behind that 273 crank. You either have to make a custom converter, or, change the front pump assembly to the earlier 273 converter (with a 904 trans). With a 727, a custom converter is about the only way to go short of machining the end of the crank for the larger diameter converter hub.