I finally got my T5048 to boot off an INSTALL kernel!
:)

After about 30+ hours of trial and error, I arrived at an install kernel 
that will finally boot this !#$ eMachine T5048 (D102GGC2).  The  kernel 
is  bootfloppy-tiny, with the 2 lines added:

options     REALBASEMEM=638        # size of base memory
options     REALEXTMEM=100000    # size of extended memory

I have 512 MB, but I didn't know what settings would work, so I chose 
small numbers.  My working NetBSD machine (an IBM NetVista 2292) reports 
base mem as 638 kb, so I used that.  The T5048 (D102GGC2) reports 639 kb 
by the boot loader.

Now I face the arduous task of converting my INSTALL_TINY kernel file 
into the standard Install file.  The INSTALL kernel with 2 lines added 
still restarts.
:(

Did I just find an install bug?
 
This solution was found on the following netbsd archive post.

list port-amd64; date 11/07/2005;  subject: Pentium Extreme Edition + 
D955XBK; from: Tomokatsu HAYAKAWA

Kenneth Freidank wrote:
> Thanks guys.  I will try that.  My next step will be to create a 
> series of custom floppies on my good NetBSD machine with different 
> kernels, until I find a kernel that works on my T5048 (D102GGC2).
>
> David Laight wrote:
>> On Wed, Jan 10, 2007 at 03:19:43PM -0500, Steven M. Bellovin wrote:
>>  
>>> I suspect a bad interaction with some device on your machine.  I think
>>> you should try booting a very minimal kernel and then adding devices,
>>> one by one, until you find it.  INSTALL_TINY or GENERIC_TINY might be a
>>> good starting point.
>>>
>>> The other, completely different approach, is to boot GENERIC.MPACPI,
>>> since there have been reports of machines that won't boot without ACPI
>>> support active.
>>>     
>>
>> Maybe even GENERIC.LAPTOP ...
>>
>>     David
>>