170 vs. 225 Swap

In my '63 Dart, I have installed a very tired original 170 with more than 150k. I also have a rebuilt 225 with about 2k on it that came out of a wrecked '71 Valiant. What are the chances the '71 225 is a direct swap for the '61 170 (bolt directly to the '63 transmission and torque converter)? How can I tell without actually pulling the engine? You guys are great. Thanks for the help.