about 3 months ago i bought an 85 camaro for a project car i had big plans for it but i bought a house and it has now become my work car

Last night on my way home form work, (about 15 minute drive) the engine started to smoke. a few blocks from home it stalled a few times and i barely got her in my garage. It almost sounded like a deisel engine. first thought was my waterpump but I have plenty of water and antifreeze and there is good waterflo thrue the radiator. I had noticed a top end tap/knocking noise a while back on the rear driver side under the valve covers. and now im getting some white smoke out of my tail pipes. The car had been driving fine untill we had our first extremely warm day then this happens. Im really hoping its not my head gaskets cuz i cannot afford that right now. Other than that possibility what can i do to narrow down what the problems is?