From what I know, PD didn't make a 7300 Series. Their model numbers consist of, the first 2 numbers are the "Series". The second two numbers are the AMPS of the unit..... at least in recent years.
Below are the claimed Discontinued Converters they have produced.
PD684 and PD685 PD6900 (Dual) PD694, 696, 698, 699, 6995
PD703 thru PD705 PD688 PD709
PD710 and PD711 PD707 and PD708 PD6800 series
PD6900 (Single) PD712 PD9000 series
If you don't get a specific answer, you can always call:
Progressive Dynamics, Inc.
507 Industrial Road
Marshall, MI USA 49068