Keep the 65. It is worth more; it is more interesting, better market too. A late 70's Z28 would have to DAMN NICE to do a trade... other wise you can pick them up all day long here in Oregon for 3 to 6K... they usually need a interior, dash is usually bad, motors are the low compression (as you noted), they just don't bring 70 to 73' type values. Your truck is too nice to give it up for this car I think.