That 2.6 V/6 doesnt sound very good to me.I dont see where you would gain anything over the original 216 or 235. I would go with a 350,yeah I know a lot of people here think the 350 is a boring engine. But lets look at the facts. They can be bought fairly cheap,they are easy to work on,and parts are readily available for them.There is definitly a reason why so many hot rodders use the 350.I have a 1974 350 in my 1955 2nd series coupled to a 700R4 trans.and stock 3.90 rearend. I baby the [censored]out of this truck,but when that rare occasion arises and I get the urge to mash the gas pedal,she will get up and go.It also gets 20 MPG.