Sorry to hear your S65 motor is seized up. I have personal experience with the business at the first link below. I think the other two are worth calling as well. If the crank is damaged a new one will need to be sourced. Could always get a 4.2L or 4.4L stroker from Carbahn too. Let us know what direction you decide to go in.
https://trueautomotive.com/lawrenceville/
https://buckhead-imports.com/bmw-engine-repairs/
https://www.ebay.com/itm/22260224395...mis&media=MORE