New Member; New Old Truck; I recently purchased and have been rebuilding and using a 1962 v6 305d model 3000 12' stacked bed with dual cylinder Dump....

Completely original untouched except by Mother Nature. Im not for sure what Oil I should be using in the Motor I have tried 5w 20 synthetic for a motor flush maybe an hour of idle time then changed to 10w 40 currently in use. I have replaced all the wood flooring and runners with pressure treated yellow wood. Greased and replaced all fluids on entire truck. Runs and Drives great Dumps with ease but after 30 min or so she starts to smoke im guessing passed the rings but it doesn't effect the truck still idles at 500 rpm??? Also I replaced All the brake pads and rebuilt the front wheel cylinders. I replace the back brake pads but the wheel cylinder kits where wrong so they still Leak. Anyone know where I can get the correct rear wheel cylinder kit?
Thanks for any help you can give