As far as i know there isn't a 4v head for a 302. They difference was a bigger cam and higher compresstion. All you need to do is change the intake. I went with a cheaper performer without the EGR passage. that steped up to get rid of my non-working EGR vavle. That means that you can take out all the of the temp vac. valves and just route the vac advance to the ported vac and the PCV vavle to constant vac.
In 68, the 289 heads were large D chamber affairs instead of the smaller heart shaped chambers. These had lower compression. Not really a big deal. With todays gas, you don't want a ridiculous amount of compression anyway. The only real difference between a 2V and 4V motor was the pistons: dished in a 2V, flat top in a 4V. The intake swap is easy and rewarding. Watch the gasket orientation like Sharkmouth said, and depending on preference you can use the leaky cork gaskets for the front and rear, or clean the surfaces with alcohol and just use RTV. (Can't tell my preference from that )