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thanks, good to know Given that, it kinda makes the idea of commissioning someone like Vito's to build a minimum order of 500 with huge upfront cost less appealing.

I wonder if these guys would ever make a run of RD400 if contacted? They do a LOT of 250/350 new cranks. I even bought 2 of them and they look really well made- but haven't installed yet to rate them.

https://www.ebay.com/itm/364763626092

Just out of curiosity, have you weighed the Vito's crank vs an oem RD crank? It must obviously be lighter, but by how much?

Stock alternator? Ported engine/ chambers?
The heavy stock rotor combined with higher rpm would cause more problematic crank dynamics, from what I understand.
TZ's had much lighter rotors...

and recess for the o ring, etc. hard to find a shop here to do it. i can do it and it was easier to find different tubes

I never did that on FZ/ FZR fork tubes, but did it on a pair of extended ("chopper") fork tubes for a 72-76 XS 650, for use on my RD. And on a Suzuki GN125 that I modified to a more "standard" stance. Both were straightforward, since the O-rings were in the top plugs.

i still have it. the stem is the right size but too long. swap the rd/fzr stem, mod the steering stops and its good. the forks stick up about 2" thru the tree.  however, theres a year or 2 fjr 600 fork tube that swaps in thats shorter. i have those in mine but can not remember the year

Shortening fork tubes is pretty straightforward. Cut off the excess at the top, then into the lathe for machining and single point threading.

what are the advantages of goin to a 520 chain

You are asking the wrong question.

Rather: What is the point of 530 chain and sprocket on a 50 year old 350-400?

Answer: None whatsoever. 520 is fine on 100 hp bikes. So perfectly fine on even the hottest RD.

I also suspect that using the stock brake light switch may increase lever travel a bit, and also make bleeding more difficult by potentially trapping air bubbles.

I had big problems when trying to use some "anti squeal" shims that came with a set of new pads. Binned them, and all was good.
My setup is an alloy repop caliper from EC, one piece steel braided teflon hose, 13 mm Brembo master cylinder, coffin style reservoir. Works great!

ill take the 300hp h2r for 50k. that's ridiculous

However,  the H2R is a porker compared to the Ducati....

I have a set of snowmobile VM34s and they are small body - not as small as a 28 but much shorter than a regular VM34.

The bad news is that they have zinc or Mazak bodies so they are a touch overweight.

Hmm, I have come across the opposite weight phenomenon. For example, the OEM VM28 for RD350 seem pretty heavy for their size, while a single VM34 or 36 from a fan cooled Rotax 503 snowmobile engine was amazingly lightweight. Almost so you would suspect it was magnesium...
Does anyone know what material genuine aftermarket Mikuni carbs are made of?

Hmm, at least to my eyes, those PWKs look more "streamlined" on the air filter side than the stock VM28s. I wonder if anyone has done any flow testing of VMs  vs PWKs?

Yes, Vm34 short bodies.

So you have tested? Equal size?

A slightly different issue regarding Mikuni carbs: Some VM30 used as OEM in snowmobiles, had same body as VM26/28. While those normally available in the aftermarket shared body size with VM32/34

Hmm, at least to my eyes, those PWKs look more "streamlined" on the air filter side than the stock VM28s. I wonder if anyone has done any flow testing of VMs  vs PWKs?

XS650 kickstarter has same splines as 73-75 RD 350, if that helps. Quite a bit more heavy duty than the RD kickstarter.
I also have an awkwardly shaped, alloy kickstarter with RD/ XS splines, I believe from a Yamaha MXer

Quite a story, and kudos for not giving up!
I actually have an ongoing XT 250 project myself, it is an "86" model, but I believe they just made too many of them in 80-82.
Anyway, it sort of must be the dad/ granddad of the 225. Very similar stroke, just a 75 mm bore instead of 70 mm.
We actually had another XT250 back in the 90s, and it gave similar fuel economy, 3 l/100 km or around 78 mpg (US). So a great little runabout for daily errands.
Talking about "errand mules", a Honda NC 750 X would be very hard to beat, even when larger, heavier and more expensive. Similar, ridiculously low fuel consumption, plenty of power for any freeway, and a super convenient "trunk" where you would expect the fuel tank to be
Beautiful? No, but darn practical

Why is it quicker? I mean is it quicker revving due to a shorter stroke? Is the three piston design attributable?...seems like more rotating mass. Is it a better design in terms of combustion design?

The early H1 had 60 hp, vs the T500's 47 hp. Both manufacturer's numbers.
Being a triple the H1 had a shorter stroke, so could safetly rev higher. More revs gives more power. So the H1 was given more extreme port timing/ cylinder design, and an exhaust system designed for higher revs and more power. I believe the H1 exhaust actually was expansion Chambers, "hidden" inside more traditional looking mufflers.

Was it really capable of a 13.20 quarter mile? That couldn't have been much slower than a H1/ Mach III?