the 429 and the 460 are the same motor, same 4.360 bore.....the difference is in the stroke.
the 429 had a 3.59 stoke and the 460 has the 3.85 inch stroke.
If its a D0VE D1VE block.....1970 the D for 70's and 0 and 1 as the exact 70's year (70, 71)
If you have D0VE or D1VE heads, these are the 10.5:1 compression....motor would be rated at 360HP
If you have the D2VE, D3VE heads....D2VE have the 8.5:1 compression and the D3VE have the 8:1 Compression. It would bring the HP down to about 212HP & 200HP.

with out changing the heads, if you change the cam to a Comp Cam 256 or Summit Racing 262, change the original retarded timing chain, you will add about 100 HP and it will breath much better.
these blocks are capable to withstand 1200-1500HP all depends on how deep your pockets are.

I spent 1500$ on Summit Racing parts on my 460 and now has an estimated 525HP. I have a D0VE Block with D0VE heads.....original rating of 365HP

Hope this helps some as well