MOST rigs today have more tow capacity than they did when I first bought a new rig in 81. An 8 lug 2500 came with typically a 300CI I6 with maybe 105-110hp and 250-300 lb ft of torque. A BB had 200hp and just over 300 lb ft of torque. Today std motors in an 8lug rig seem to have 250-300hp, and mid 300 lbs of torque, with diesel options of 300-400hp and upwards of 800 lb ft of torque. Since tow capacity is more or less based on power, yes, ANY rig today has more potential than in the past.
BUT< one still has to deal with what the chassis can handle, or how much payload you have to work with. Even then, a typical 8lug rig has more payload today than they did in the past, so again, more potential for the ability to tow a higher wt trailer. This is also true of the 5 or 6 lug half tons too. Even the mini trucks have motors that are bigger and better than the 76 toyota I had back in HS.
I do not know what you are towing, I have my own personal limits to tow with a given truck. It is not what the manufactures rate things at. SOme cases I am lower, others higher. I'll personally go to about 2x the GRAWR of a given rig. I find that over this amount, the trailer starts to wag the truck per say in some instances. So for a typical 8 lug 2500, with a 6100-6800 RA, that is about 12-14K lbs of trailer. SOme are rated to over this. One can pull over this and be safe! That is just my personal limit. I would have no issues pulling that with todays SB8 motors either. As the trannies are better, motor stronger etc than BB motors of yor!
Marty