Bill,
Wow, even cooler. I didn't realize he was running it without the fairing again.
Pete,
You got it. The breakdown is chassis first, then motor, then fuel type. The A designates Altered frame. PS is Partially Streamlined. P is Pushrod motor. And the G is Gasoline.
The frame is an early 70's Triumph 650/750 oil in frame chassis. Martin completely removed the forward down tubes and replaced them with a single bolt in piece. He also sectioned out a few inches from the vertical oil tube to lower the bike. What he removed from the vertical portion of the frame he then sectioned into the tube under the tank in order to lengthen the chassis. Clever boy.