I hate to say this, but the RRC/D1/D90 steering box actually loves the Lucas stop leak stuff. I've had several D1/RRC's over the years and normally when I buy them the PS system is a leaking mess. I drain out the fluid from the reservoir and add the Lucas stuff and after several warmup cycles (as it goes thru the entire system and blends with the PS fluid) the PS box is no longer leaking. I think it's 9.00 a bottle, but I've had good results with it and RRC/D1/D90 PS boxes.
This special stop leak fluid seems to make old seals softer, and lasts a lot of time. If there is enough wear that allows to drop fluid drawing trajectory on floor, then is necessary to change torringtons and seals.