Questions on replacing wall mount toilets

Hello,

I have a question on replacing some wall hung toilets. The units are the originals from the house, stamped with manufacturing dates from 1969. They appear to have a standard wall mount bolt arrangement (4 bolts square pattern, 9" apart width, 7 1/2" apart height, 5/8th bolts). The bottom bolts (and presumably the drain center) are 4 1/4" high off the floor. I am looking for a few things in the replacements.



1) The city of Austin rebates HET toilets (1.28 or less) $150 per unit and 1.6gpf $75 per unit. I would prefer dual flush HET toilets both for the higher rebate and the water savings.
2) I would like to have at least 16 1/2 rim height.
3) Elongated bowl.
4) Works with standard residential water supply, I don't have the plumbing to support a commercial flush valve.


So far, here is what I can find:

American Standard Glenwall and Eljer Walford - It looks like these toilets will have a very low rim height with my current wall mounts.

Crane Rexmont - Rim height is good, but still only 1.6 GPF and seems to have bad reputation for flush performance.

So it looks like I'm out of luck in looking for a wall mount HET, or even a wallmount with good flush performance that will not be too low to the floor. I am assuming that moving the drain and mounts higher would be a substantial project.

So here is part 2 of my question. How hard is it for a plumber to install a rear discharge floor mount toilet where a wall mount used to be? It looks like the drain is already in the right place, but the mounting bolts are much narrower. Also is there a different type of flange on a rear discharge vs wall mount? If I can mount a Gerber DF-21-325, it looks like I'll hit all four of my criteria - I just would like some idea of the feasibility of the swap.

Thanks in advance for any feedback!


American Standard Glenwall

FYI: We have two Glenwalls in the upstairs bathrooms which work quite well.

toilets

With a wall mount toilet, you just raise the opening if you want a different rim height, so they do not make "ADA" specification toilets for them. The floor mount rear outlets use a floor type flange on the wall with a pipe replacing the current stub.

HET toilets ( 1.28 GPF ) are an emerging technology. The variety of available models is limited at this time.

California has passed a mandated 1.3 GPF law. Beginning in Jan 2008, it will be phased in, requiring manufacturers to have a certain % of their production meeting the new spec. 100% mandatory in 2010. With about 10% of the entire population of the US living in California, things like this tend to have national impact. You can expect to start seeing a lot more of these models.

Thanks for the replies so far!

With existing construction consisting of tile walls with cast iron drain pipes, I figure that raising the drain opening would be a fairly complex and pricey endeavor. Even if I do, I'm stuck with more expensive toilets with less rebate from the city. If I go rear discharge I can get get Gerber Ultra Dual flush for cheaper and w/ a bigger rebate. But I don't know what is involved in converting to a different fixture style - the drain is already at the right height, can I just install a flange?

Which do you guys think is easier - raising the carrier in the wall for a taller wall mount or replacing the wall stub with a flange for an ADA rear discharge?