As an expert in this field (T-boned, rolled, bent the top of the steering wheel down almost to the dash, and totaled my '57 while wearing a 3 point belt - just had a small scrape on my left elbow), I'd advise 3 point belts. I got mine from these guys, and after testing them in my '57 (picture below) put a set from them in my '52 replacement for the '57. Good service and the product passed my testing.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12 '52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
