what yr is my 273??

I also understand that 1968 was the year Mopar changed to the larger crankshaft pilot hole for the torque converter. At least they did for the 318 SB. Search if also true of the 273. If so, and you have the original tranny (cable shift) w/ original torque converter (fits original 18-spline input shaft), whoever installed the 68 engine should have put a special spacer ring over the torque converter's snout so it centered on the crank.