I have a '90 chevy truck brochure that has all the trucks specs.
The 305 has a whoppin' 175 hp and 275 ft lb torque.
Your trucks GVWR and FAWR and RAWR will be on the drivers side certification placard.
Those old short bed trucks were pretty light and payloads ran in the 1300-1600 lb range. As one poster mentioned using higher rated tires I would add the trucks wheels may need to be upgraded to take advantage of the D load range tire higher load and pressure rating. You may want to add air bags or Supersprings to the rear suspension "IF" it sags too much.
However much depends on the TC actual weight. We have lots of TC owners so maybe some one owns one and can help with its actual weight.