I have an SSD working in the original EIV using an ACARD ARS-2000SUP Ultra SCSI Hard Disk Drive. This is a 3.5" sized case with an internal 50 pin SCSI port to connect to the internal SCSI port in the E4. It has a SATA connector on the bridge board (SCSI to SATA) which accepts a 2.5" laptop sized drive. I installed a Samsung 830 Series 64GB SSD. Please note, the EIV is running EOS 4.62 because EOS 3.0 (machines stuck with a 1MB CPU FLASH) can't use a drive larger than about 9GB. If reading this thread please remember i'm talking about the original classic EIV which doesn't have IDE ATA, it has only SCSI that is why this works. This should also work in the Coldfire E4 Ultra's since they also have a SCSI internal port and I will test in an Ultra at a later time.
This solution maybe seen as expensive to some, and one would have to make that determination themselves. I paid $200 AUD for the ACARD ARS-2000SUP and less than $100 AUD for the Samsung 830 64GB SSD. I bought mine locally and it was posted from ACARD in Taiwan direct to me. There is a place in the USA that has this quite cheap http://www.mars-tech.com/ars-2000su.htm
I changed the jumpers. I removed the jumper on "Parity Enable" so it was open and disabled, Removed Termination Power jumper, so that the EIV's term power is used and put a jumper on SCSI ID 1. The drive is visible to the EIV and after a format it the full info was available. The SCSI bus is scanned at lightening speed BTW. I'll attach some pics. I haven't saved any banks yet so I can't give any impressions of performance.