Welcome. Neither of the trucks you mention should be used to pull a 3 horse trailer. You need to upgrade your research to 3/4 or 1 ton models. The Chevy 3600 or 3800 or GMC equivalent would do the job. Since this is a GM truck site the Ford shouldn’t even be included in the discussion. If starting with a mechanically sound fairly rust free truck your restoration timeline would be 6 months to a year for a good all round mechanic. Budget not including original purchase price of the truck would be $5000 to $25000 depending on the level of restoration and amount of work you could do yourself. Upgrades for safety and convenience could include disc power brake conversion, seat belts, power steering and of course air conditioning. Engine and suspension upgrades raise the cost significantly.
Good luck on your imaginary journey.
