What cover crops are the best for wheat stubble?

What works to be seeded around July 4 in preparation for planting corn the following spring.

Back in the day we frost seeded clover, sometimes Mammoth Red sometimes Yellow Blossom Sweet.

Maybe blend some Alsike or Timothy.

That was when we planted 1.1 M population wheat.

1.6 M and full fertilizer does not work good with frost seeded clover.