In 1948, aged 18 years, Wheelahan began providing fill-ins, covers, short features and stories for Fiction House reprints by H. John Edwards. He did some covers for Archie reprints, signed just as 'P'.

He later worked extensively for Youngs Merchandising Co., initially inking Stanly Pitt on Yarmak (1953-1954) before creating that company's Davy Crockett series (1955), The Raven (1957) and The Panther (1957)--which ran for 73 issues at a time when the local comics industry was in decline. In 1957 he also produced Rex Strong for Magazine Management (Approved Publications).

From the mid 1960s to 1996, Wheelahan wrote more than 500 western, romance and detective stories for Cleveland Publishing under several pseudonyms, including E. Jefferson Clay, Emerson Dodge, Ben Jefferson and Brett McKinley.

Wheelahan created and wrote the children's TV series Runaway Island (1982). He wrote several episodes of A Country Practice and was commissioned to collaborate with Michael Laurence on a sequel to the TV mini-series Return to Eden, which was never produced.

Taking control of his own work, Wheelahan set up Dodge Publishing and released three self-published novels (Savage Texas, Arizona Psycho and Sons of Cain) before moving to the Black Horse Western imprint of British publisher, Robert Hale. He began work on his autobiography, to be titled after his first Cleveland story Never Ride Back.