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You don't necessarily need new heads unless that is just what you want to do and have the money to do it.
For a street build toy the factory iron is fine and can be made better with some minimal work. If you have your heads checked and the guides and or seats are trashed, then maybe you spend the money on new or find a good used set to use as cores.
If it were me doing a basic low compression rebuild I would not spend a pile of money on heads. If you do need some though the speedmaster heads usually go on sale at a big discount around Thanksgiving. They still would need to be checked out though by someone to make sure they are set up properly.
You can do a basic check by setting them chamber side up and fill each chamber with alcohol, gas, or whatever liquid. If the valve job wont hold liquid in the chamber then it wont seal air either and will need attention. Before installing any heads they need to be taken apart and cleaned well.
