We towed a 1966
Overlander with a 1975 Ford Custom 500 that had a 400cid small block V8. It did not come with a tow package and we did a number of upgrades to the vehicle.
When you say that your Caddy doesn't have a tow package, you must assess what a tow package may include:
1) tranny cooler
2) oil cooler
3) greater capacity/chambered radiator/electronic fan for cooling.
4) upgraded shocks/airbags
5) wiring for trailer lights/brakes
6) brake controller
7) hitch receiver
With our 75 Ford, we basically did all of the above except for #4. We did use an equilizer hitch with anti-sway.
Your car's braking capacity is another consideration - if the trailer brakes fail, could your car cope with the extra weight in that emergency.
You can probably tow anything - these upgrades add to the enjoyment & success of the experience!