Question on towing and load capacity

[McDeezl]

Currently in the process of building my '72 GMC 1/2 ton 2WD, LB-FS
Has a brand new 350 crate engine (330 HP) and TH400 with a 3.08 rear end upgraded to an Eaton posi. Put new HD variable coils in the back.
Trying to find info on capacities for these old trucks and specifically for towing and there ain't much out there.
I realize that the 3.08 won't really cut it for towing and I can correct that easy enough, the powertrain has more than enough balls but here's the question ....
How do the 67-72 pickups compare to today's pickups in terms of towing capacity? Same, better, worse?
Looking to get a travel trailer next year rated for 1/2 ton compatible but would still like to keep it at the low end, say under 5,000 lbs and under 700 lbs hitch weight.
Will probably end up buying a new GMC 1500 SLT 4x4 with a towing package at the same time but just curious whether the '72 would hold up or not despite passing everything on the road except a gas station!

Feedback is appreciated!

Tks

Sean