There was an article in QST, Sept 79 by DeMaw on a conversion. A refinement of the project is in the 1984 ARRL handbook (and perhaps other). The modified amp operated on 160, 80 and 40M. It used a broadband toroidal input circuit and a Pi output. If you can't find a handbook with the article, send me an email and I'll provide additional details. 73 Tom KE6FI