My D1 is on 35s and runs a modified steering system with a P38 pump driving a PSC hydro assist (still has the stock box, but a ram to help with the turning).
I've not been totally happy with this. First, I cooked a pump last year. Then last month I had the new (junk yard) pump start to flake out as well. Additionally I've felt I had enough pressure but not enough volume out of the Rover pump because turning at a normal rate the hydro worked fine but trying to turn quickly and I wouldn't have enough boost to keep up with it and the steering would go momentarily hard.
Lastly I had a bit of a leak at the reservoir making a mess.
So today I swapped the pump out for a GM 'canned ham' pump as used on just about everything in the 70s and 80s. Even some Mopar stuff used this pump. It's super common and works well.
Although you could certainly sort it out yourself, figure out the right pump (lots of variations), swap the pulley, make some brackets, find all the appropriate adapters for the plumbing, etc, I took the easy but more expensive way and ordered a kit from Nick Markiw on Defender Source. He's just down in SoCal so it was easy enough.
I did have to make some small tweaks as my truck isn't stock; I had to gently bend the return pipe on the pump to clear my aftermarket shock towers and although the kit came with an adapter and hose to plump the return direct from the steering box I have a cooler so my run is different and I had to pick up a few feet of hose to complete the installation. Over all it went in pretty easily and it seems to have plenty of power driving around the yard/driveway. Nick actually didn't think I'd even need the PSC ram anymore as he's run this pump with 35s himself, but it's not like I'm going to get rid of it...you know 37s are going to happen eventually.
Here are a couple pics, along with a link to a better write-up of the installation than I could do.