Compression of at least 9.5:1 and airflow will get you there.

906 heads flow a little better stock than most of the others if you have a choice. Use the thin .020 steel shim gaskets and mill them to keep compression up. 915's are nice too but harder to find.

An aftermarket intake, headers, cam and a Holley 3310 will also help.

Look for deals as $2k doesn't go very far. Lots of guys upgrading to aftermarket aluminum heads so good cast iron ones are pretty cheap right now.