I vote for the 305 .If the cam has a flat spot causing the miss, you need to check it out first.Identify which cylinder,check the valve train,replace the cam,if you have to. Don't even pull the heads unless something big shows up. If it only has 70k miles,it should still be like new.Maybe your miss is ignition. I was faced with the same problem as you for my project.After checking costs of rebuilders, a G.M. 290 horse crate motor was the best buy on a fresh motor.Has about 3 yrs. warrenty insead of about 6 months from most rebuilders around here.A long block for $600 sounds to cheap to have much machining put into it.Maybe a honing, cheap rings, and bearings, a cheap cam and lifters, but nice rattlecan paint on the outside.The G.M. crate mtor is closer to $2000.00. That was more than I wanted to spend at this time.I ended up buying a Chev Impala with a 305 with air that ran like a top for $225.00.Drove it around the farm for a couple of weeks to check it out, then pulled both motor and trans, put into my project.Has a small block chevy.305---350 I don't care.If it worked in an Impala with air, it should have enough power to let me cruise around in a 39 Chevy.
