LOL as if anything you say about any other bike than your wr450 matters. u admittedly have no experience on anything but that bike in the last 25 years. that 350 would run circles around your wr frankenbike.
Oh, and by the way:
39 bikes since 1999
Riding since 1971 !
There is NO SUCH THING as a great stock bike.
They all suck in one way or another and must be upgraded/adpated to the rider/situation.
...unless of course you suck as a rider, or if you are an expert, don't mind wearing out a bike in one race.
Your precious KTM bikes used by Pros have just as much money spent on them (about $40k for SX, about $20k for offroad) as any other brand, to make them competitive at a professional level.