One year, 1969, out of protest because Chrysler insisted he continue to run Plymouths while Dodge drivers got the superior Charger Daytona. Petty would get his winged Road Runner Superbird for 1970.
As for the hauler, you used whatever would get you from race to race to race. Brand loyalties didn't run that deep.
Petty Enterprises ran Ford for one season after an argument with Plymouth. Richard wanted to switch to Chargers for 1969 and Plymouth said "No, you are a Plymouth driver". Richard responded telling them noone was going to tell him what he could and could not drive. He went across the street (as he put it) and struck a deal with Ford. Realising thier mistake, Plymouth created the Superbird for 1970 specially for Richard Petty. It worked and he came back to Plymouth in 1970.
As for the Kit car. No brand loyalties don't run that deep, bur Richard was all Chrysler in 1972 when they had the Dart. It was hauled by a Dodge truck. When AMT paired the Dart kit with the Ford hauler Lee blew his stack and made AMT pull the kit from production. This is why the combo kit is so rare. Being a very easy going sort Richard was just going to let it go, but his mother Elisabeth held the purse strings for the team and she urged Lee to take care of it (as if he wasn't already on it) and get the kit production stopped. If AMT does re-issue the combo Lee will be turning over in his grave.