Think of 402 as a "30-over 396 with a weak crankshaft". The main difference between 396 and 402 is the "cast" crankshaft in the 402. 396 had a nice forging, the same as 366 and 427. If keeping the revs under 6,000, the 402 crank is okay. A forging "drops in", as all the journals and spacing are the same.
454 makes a lot more low-end power. This is "better" for the heavy car. The 454 block is different, though, with a 1/8" larger bore size. It also has te 4" stroke to increase the displacement from 427. Non-performance 454s also have cast crankshafts. Forgings are desired for any "real" performance applications.
402 uses basically the same cylinder head as 454 of the same years. 100% interchangeable.
For a nice "cruiser", 402 is fine. It can be cammed and "tuned" to get good low-end and decent fuel economy. 454 will make more low-end power, as previously said. If response and performance are more important to you, 454 is probably the best choice.