That depends on your goals. The cheapest approach to getting more power in a decent cruiser is to find a 350 or someone's abandoned project and swap it in, it will bolt in the place of the 305 with no other changes.
If you have a reason for keeping the 305, then go for it (I've always wanted to build a stroker 305 just to tinker with some of the advantages of the small bore 305 and see if I can get around the breathing problems, but that's a different discussion).
Things to note:
- the swirlport heads will be too big for good compression if they are off a 350, but fine if they're off of a 305. If they're off a 350 you'll probably want to get them milled to get the chambers down below 60cc. FWIW the swirlport design is actually an interesting complement to the stroker 305, which should help build torque and control detonation making for a surprisingly efficient engine.
- most aftermarket heads will not fit, anything with larger than 1.94/1.50 valves will be a problem.
- What year Z28? Be aware that they will use different balancers, flywheels, some gaskets... and the later heads will use the >86 intake pattern