The OP says stock looking with under chassis headers. This isn't a concourse restoration. So it seems there is some leeway in what happens to this GTS. Stock looking would even allow a stroker kit. One thing to remember if 'stock looking' includes a year correct stock factory cast iron intake manifold, that manifold will limit airflow to around 200 cfm even if your heads flow 320 cfm. Yes, I've personally made that test.
