Camshaft suggestions

318 heads can work real good with some port work (are you up for some minor DIY porting?)(larger intake valves)
the 302 318's have smaller wedge chamber and better exhaust- intake could also use some work see posts above for stock
the EQ heads are available with shaft rockers most likely your best value
or Magnum heads with magnum lifters and pushrods
basically those are your choices without going aluminum
the piston shown is the stock (non HD truck) piston- no way to get any quench or compression with it but if you have to keep it we can do the best we can
I would not buy 360 heads and start there- money pit with no future big chambers etc