Thanks Geoff, that T500 race bike looks the business, I'd love to take something like that for a lap or two of Phillip Island, back in the 1990's the Army had a bit of bad PR when several young soldiers were killed in bike crashes, so they paid for everyone in the Army to attend advanced motorcycle training, which, apart from the usual nit picking #$%* from the instructors like, "Don't use your mirror for a helmet holder" and the usual "death by statistics" that all public speakers like to espouse, usually to kill time, it was a great activity, with a full day at Phillip Island caning our bikes mercilessly while the instructors yelled unintelligible instructions to us, which most of us ignored anyway. I was riding my old 1979 BMW R100RS and scaring everyone behind me as I wobbled and wallowed around each corner, showering them with sparks, but I didn't fall off, and recorded a top speed of 130 MPH down the main straight, just before I slowed down to wobble and wallow around turn one. Great days.
The T350 was a sneaky little bike, it was pretty much a bored out 250, as you said, to only 315cc, but Suzuki went to town with 32mm carbs (up from 24mm on the T250) along with much bigger ports. I bought a pair of T250 cylinders when it looked like Keith wasn't gonna be able to find some good T350 barrels, and I was surprised that the carb spacing wouldn't allow the much bigger carbs.
Back in the day, the Castrol 6 Hour was a fantastic production race, 6 hours of flogging "stock as a rock" bikes around a nice tight circuit at Amaroo Park in Sydney. In 1972, Joe Eastmure achieved legendary status when he beat Honda, Kawasaki and Ducati 750's, not to mention Yamaha RD350's etc to win the race outright on his T350, only to have the results overturned by appeal. It's a great story, and really sums up the T350, a little bike that punched well above it's weight.
https://www.motorcyclealliance.com.au/joe-eastmure-best-six-hour-racer-youve-never-heard/