1952 Chevy with Small Block overheating

[48fordf1]

I have a 52 panel truck with a camaro subframe, new Chevy crate 350 rated at 260HP, with a holley projection 2d fuel injection. Its coupled with a TH400 transmission and a3.23 rear end, with 205/75 R15 tires. It runs down the road at 60 mph at 2500 rpm. Additionally it has a Walker Z series radiator with a 16" electric puller fan with about 3000 cfm i also have a condenser fan.

When I pull a small camper (1500lbs), it will want to run up to 220F without air running. I have taken my mechanical advance and vacuum advance from about 47 degrees to about 30, in addition to the 10 degrees BTDC it idles at, but it still runs hot. I have a rich/lean indicator that stays in the green.Additionally, it gets about 8mpg. I was thinking with fuel injection I would get about 15.

I purchased a aluminum 3 core radiator, but dont want to install it and it not make a difference.

Anyone have any ideas i can check. I have a limited distance between my waterpump pulley and radiator, so a thick fan wont fit.
Thanks