Swing Arm or Leaf Spring for towing?

[RUSSOM]

I'm interested in buying a 67-72 truck but I'm concerned about the swing arm/coil spring rear suspension versus the much rarer, for these years, leaf spring for towing. I'd rather have the 67-72, the 73+ trucks look to modern for me, but being able to tow this trailer is a must and I need the truck to have the ability to tow it safely. The trailer is an open type, total trailer & car weight is 7K. I'll be installing a gen 3 engine so I know I'm not limited on power, just very concerned about truck and rear suspension. Any thoughts?

TIA