Converting Toto 1.6 toilets to 1.28

Hi, I was lucky enough to find a new (display) Toto Supreme ebony toilet (at a great bargain price) at a plumbing warehouse and I was wondering if this toilet could be converted to a 1.28 gallon flush by just replacing the flush assembly and flapper. If it is that easy, does anyone know if I could do the same to a Toto Ultimate, as I can get one of these pretty cheap, too. Lastly, I see many threads recommending the Korky fill valves and red/blue flappers, but I only see one fill valve at Lowes. Does this one fill valve work for most, if not all, Toto toilets? I do note there are many different models of fill valves listed for each Totos, either Power Gravity, Emax or Gmax. Do they all use the same replacement?
Any help is appreciated. Thanks.

IF it were that easy, there would only be 1.28 toilets, and they would be the same price as the 1.6 ones. Your idea would be the equivalent of when manufacturers tried to convert 3.5 toilets to 1.6 models by just making minor changes. That was a disaster, and your plan will be also.

Well, I got the idea from reading one of these threads where someone stated the Toto Drake bowl can use either the 1.28 or 1.6 tank. Anyway, saving 1/3 gal isn't all that big compared to the savings for the toilet (pd < $250). I'd appreciate any advice on the latter part of my post regarding the Korky replacement fill valves.
Thanks again.

For the 1.28 gallon parts to work, you need to make sure the bowl matches.
Some of the older bowls hold more water.
In the Toto line, the 1.28 bowls have a E in the numbering system.

I personally think that the 1.6 is fine, or the 1.28 work just fine as they are.
I wouldn't bother changing things.

Most of what the 1.28 does, is to make sure it doesn't overfill the bowl.
I've seen some replacement fill valves pour an extra 2.0 gallons down the drain, after the flush has takeen place, and the bowl has refilled.
Some will continue to overfill for a minute or two.