At least according to this fairly detailed eBay listing you might be limited in what GPUs you can run in an R730. It states a 300w max per card and double width, which would eliminate both the power and physical requirements of the 3090/4090. You could run say some Tesla P40s but they would be a bit slower.
Another option would to be just buy a rack mount 4U case and say a X99 motherboard (same era CPU as the R730) which would give you a bit more flexibility in running 3090/4090 cards so long as you had a 1200w or so PSU.
https://www.ebay.com/itm/364128788438?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=XkOKzd0RR_6&sssrc=4429486&ssuid=9jfKf00cSoK&var=&widget_ver=artemis&media=COPY
At least according to this fairly detailed eBay listing you might be limited in what GPUs you can run in an R730. It states a 300w max per card and double width, which would eliminate both the power and physical requirements of the 3090/4090. You could run say some Tesla P40s but they would be a bit slower.
Another option would to be just buy a rack mount 4U case and say a X99 motherboard (same era CPU as the R730) which would give you a bit more flexibility in running 3090/4090 cards so long as you had a 1200w or so PSU.