You know my thoughts on this. I've done a few 71 - 73 stangs with 429s. I like this engine combo in a light vehicle. 429s will rev to 7,000 rpm with big cam -no problem.
Low end torque is not brutal
,
The 460 is a good motor also. It has a longer stroke than the 429 and the same bore. Either will work well. 460 has brutal
low end torque. It's not a bad thing --just hard on tires.
Remember the 71-73 mustangs came with 429s.
I have a set of early 429 close cambered heads and 4 bl intake at my shop that I have had for 25+ years.
Just cause closed chamber is the best and are very hard to come by.
Being either are early 70s style it comes to the heads. If either one has the small chambers then it's a toss up. If one is open chamber and one is closed chamber, the closed chamber is the one to get.
Remember our little talk about FORD heads at the park?