There are too many variables that come into play to give any "real" estimate. Stock? What do you mean by stock? What's good for one motor isn't good for another. This is comparing apples to oranges. But between a 302 and a 306 there's about 6hp difference...
ok heres the dyno numbers. Its a bone stock 95 5.0 automatic, then everything was transfered over onto a 347:
...........RWHP........... RPM......302........347
3700.....168........191
3900.....173........194
4100.....176........200
4300.....174........198
4500.....174........193
4700.....171........188
4800.....168........186
---------------------
...........RWTQ........... RPM......302........347
3700.....238........271
3900.....233........261
4100.....221........256
4300.....204........242
4500.....191........225
4700.....176........210
4800.....171........204
Hope that helps ya. As for the 331, it'll probably almost look like the 347, just proportionately smaller (about 5% less power all around). Remember, these numbers are from an automatic.
ok heres the dyno numbers. Its a bone stock 95 5.0 automatic, then everything was transfered over onto a 347:
...........RWHP........... RPM......302........347
3700.....168........191
3900.....173........194
4100.....176........200
4300.....174........198
4500.....174........193
4700.....171........188
4800.....168........186
---------------------
...........RWTQ........... RPM......302........347
3700.....238........271
3900.....233........261
4100.....221........256
4300.....204........242
4500.....191........225
4700.....176........210
4800.....171........204
Hope that helps ya. As for the 331, it'll probably almost look like the 347, just proportionately smaller (about 5% less power all around). Remember, these numbers are from an automatic.