I cheated and got 316 CI (rounded up). How did I cheat? http://www.csgnetwork.com/cubicinchdispcalc.html

Some of the later 305s were set up for roller lifters. If your block has the treaded bosses in the lifter valley for the "spider" type retainer you can use the lifters and push rods from your V6. But you will be short four of them (four lifters and four push rods) and you will also need a V8 spider, a V8 roller lifter cam, and a special gear for your distributor.

For a daily driver truck that sees some towing I'd recommend an Edelbrock Performer cam kit. Good torque and good mileage. And not very expensive. Roller cam shafts and lifters are better than the flat tappet versions because they reduce friction and facilitate more aggressive cam grinds.