Check your headers, if they are small port and your heads are large port, there is good potential there.
Without forced induction: 10:1 pistons, bigger heads and bigger cam.
However, now you are getting into serious $ with possibly 10-15% increase in power. Depending on available funding a stroker motor (408-445" 7-12K) could be your best bang for the buck.
Look at craftperformanceengines.com for prices. You'll want to budget an additional 3K for shipping, headers, pulleys, low profile
oil pan etc.
Hope you find what works for you