Several things - the Elf has a Mk1 rack and steering arms, if you get a later rack you'll need to change the arms too. 
You may wish to depressurise the hydrolastic and uncouple the front hoses to actually do the rack swap; the hoses pull tight as you lower the back of the subframe and you end up losing knuckle skin and swearing a lot as there isn't quiiiite enough room to get the rack in & out and the U-bolts back in.

Thank you, scooperman. Of course you are right. I am in Pittsburgh. Thank you for your advice. I don’t want to have mine down for a rack rebuild. I’d rather get a rebuilt one or one to rebuild or buy new I guess. 
paul

Might help to let people know your location.  The Riley and Wolseley variants were never imported here, a lot of classic Mini owners might not know that all the Rileys and Wolseleys shared major hard parts with the early Minis;  with that info maybe someone reading this may realize they have some parts you could use. I expect your rack could swap with any of the MK1 Mini racks made by Camgears.  There were four versions in the MK1 years, but all four RHD MK1 Mini racks had the same 17H6300 pinion and 17H6376 rack gear, if those happen to be the items you need for your rebuild.

I am looking for a rebuilt (or a core to rebuild) steering rack for my RHD RILEY MKII.

PAUL