The two were arrested in March on warrants issued in Tampa, Fla., related to charges that they conspired to distribute more than 100 kilograms of marijuana.
Vowell agreed in May to plead guilty to one of two charges in return for cooperating with investigators. Prosecutors recommended a sentence on the low side of federal guidelines of 5 to 40 years in prison. And they won't oppose a request for a sentence of less than 5 years.
Sunyich pleaded guilty to both charges in the federal grand jury indictment. A third man, Florida resident Timothy Oneal Long, also changed his plea to guilty on Wednesday to both counts.
Vowell and Sunyich were questioned by Drug Enforcement Administration agents on Jan. 19 after they returned to St. George from Tampa with $166,288 in cash on Vowell's plane.
Agents said both had used a hotel room in Florida to drop off about 100 pounds of marijuana for a Florida resident who turned out to be cooperating with DEA agents.
Sentencing is set for Aug. 20.
The Piper Aerostar plane later forfeited by Vowell, a friend, neighbor and business associate of Johnson, was allegedly paid for by Johnson, according to court-appointed receiver who took over Johnson's companies after he was sued by the Federal Trade Commission in 2010 for allegedly defrauding online consumers.
The receiver claims Vowell and Johnson were linked in a plot to hide assets, including the plane, from the court.
Johnson also faces 86 criminal charges for allegedly creating a series of shell companies in order to deceive banks into continuing to process credit and debit cards after banks began to cut off his accounts because of a large number of consumer chargebacks. Johnson denies the charges.
Sunyich, his father, Steve, and siblings earlier this year also were sued by the FTC for an alleged scheme in which they bought consumers' information including credit card numbers from payday-loan companies and then began charging monthly fees without authorization.