Welcome to allpar. The 170 and 225 cubic inch engines were almost identical -- the main difference is that the 225 has a longer stroke. The engine swap should be straightforward.\n\nSwitching from a manual to an automatic will be a bit more involved, though. The automatic transmissions then had a push-button selector; if you use a column or floor shifter, it won't be original, and will involve more work. As Dana specified, you'll need a TorqueFlite 904, and the radiator should also be changed. While it can be done, I think you're better off keeping the manual.