300U power steering

I have installed the priority valve behind the control valve for the rear hitch. my lift no longer works. In an earlier post I was told the larger port was to feed the valves in reverse. In the parts book it lists a valve cover for tractors with power steering. Is this the cover I need to back feed my valve? Could I drill my exsisting cover to feed the valve. Note, my tractor was not originaly euiped with power steering. I got a power steering box but it never came with any priority valve. I got that from someone else later. This conversion has been a long project and I hope the end is in sight. Thanks to all who have helped Mark

I went on the CNH site and found the parts breakdown for my 400 when I installed the PS. There is no info but the picture was worth 1000. Geoff

markk, I`ll try to help you the best I can.I have a 300U with power steering, but mine had it on when I got it(have worked on most of the PS though).I`ll tell you how mine is.First off, it sound like you have a parts book.If thats the case,great,go to page 370.Otherwise,CaseIH has parts list online at caseih.com/parts.
It makes a difference how many valves you have on your 300.I will list by item number what you`ll need.Some parts you will need with any amount of valves,others only with certain # of valves (kind of gets a little complicated !). You for sure need (1 ea.) items 2,6 & 13 (screws in where item 14 plug is)If you only have the valve for the hitch then you use (1)item 22 elbow, if you have 2 or 3 valves,you need (1) item 23 then.To answer your question on drilling your existing plates,no, theres not enough "meat" there to get enough threads in it.With that in mind,you`ll need (1) item 16 (part # 364878R1,cover w/hole in it)for single valve set up or need (2) item 16 if you have a 2 or 3 valve setup.For a 2 or 3 valve you need (1) item 22.For 2 valves, you need (1)tube, item 18. For 3 valves you need (1) item 19. Finally, you will need (1)block off plug item 21 and (1) o-ring for block off plug, item 20. The book has a couple different sizes of plug.Common size was 1/2", but check your opening.
Looks like items 6,13,20,21,22 & possibly 23 are still available at CaseIH.Items 2,16,18 and 19 are for sure available at The Parts Depot.Your CaseIH dealer has to order from the Depot,you can`t order direct. I`ve probably got you mighty confused by now, but post again if you have questions. Good luck.
P.S. If you have any decent salvage yerds close by, check them out first. Parts from CaseIH and The Depot aren`t the cheapest!

Thanks Mark I don't have a parts book. I used the online one. It has good ilestrations but the numbers don't match up with what you gave me. My tractor has the 288 Hydraulic system listed in the hydraulic section. I am only using one valve. With the information you have gave me I should be abel to get it working.
Thanks again

markkk, your welcome. If your using the online version, dont go to the hydraulic section of the 300. You have to click on attachments and then line 370. This corresponds to the page number in the parts book. It shows an illustration of what I`m talking about and the numbers will match then. Mark