Need a 340 cam or a tich more. Port the heads and use inexpensive LS 5.3 valves. 1.9"/1.55". You do need to install either the LS powdered metal guides or bronze guides, with the 8mm diameter. That also opens the door for beehive springs, retainers and locks.
Go for it, only 22 CID difference. Just need the port flow and velocities.