My boss recently bought a Ford 8N with a bucket up front and hydraulic ... stuff off of the back.
He says he can't operate the front hydraulics until the rear is lifted to the maximum position. He also states that if he has a Dearborn model Selec-trol valve he wouldn't need to mess with the position of the rear to move the front. (If I understand him correctly.)
If you know of this valve and/or have one for sale, post up here or PM me.
Thanks, Ross
ps. What's more grassroots than a Tractor?! 
It has a priority valve that diverts oil from the back to the front when the 3 point hitch tops out and causes oil to stop flowing. The pressure overrides a spring and flows to the front. You would need to remove that valve and replace it with a 3 position (r-n-f) selector valve. But is that valve not internal? Not sure how you would get to it without splitting the tractor.
Another option would be to use a PTO operated pump and have a separate system for the front. All that stuff is available at Princess Auto in Canada, so most likely Harbor Freight or somewhere like that. The hydraulic guys at Princess really know their stuff so can make good recommendations.
He did say that he could modify the existing block, but without a backup block, he didn't want to risk ruining his only one.
Tell him he should have bought a real tractor before complaining....FWIW, you should be able to set the height on the 3 point to be lower via a lever on the right.....thus allowing the loader to be used faster. I have never heard about what you're boss is referencing.
Shouldn't a two-way valve to close off the rear (allowing over ride to the front) work the same as having the rear fully extended?
IOW, close the two-way to the rear instead of fully extending the rear whenever you need to use the front.
In reply to fasted58:
That would work, but I will bet his 3-point and loader both end up on the ground like every other 8/9n
I'm not trying to troubleshoot or solve his tractor problem, I'm trying to help him buy the part he's looking for. If it was my tractor, I'd be doing what most of you here are talking about, add a valve or whatever...
All he uses his tractor for is to maintain his food plots at his hunting land. No real farm work. Think of it as he is about to retire and he wants a sandbox toy...
Aside from a few mentions that were asking of such a device on old tractor boards, I haven't found any evidence of what he is looking for.
I'll chime back in if I find something. If it exists, it has to be easier than finding a cab for a 1930's Oliver 70.......oh wait, I've done that already. 
Thanks Yamaha, He just said to me if I find one, he will buy it. Ebay, craigslist, out of a trunk at the park... I know there are some tractor folks here so that why I post this ad.
http://www.smokstak.com/
and
http://forums.yesterdaystractors.com/index.php?sid=8f0f3bbfcf2dd4683d34939f4c5907f4
I'm no help, I don't have a loader on my Golden Jubilee.
Simplest is the auxiliary pto driven pump. Way more pressure and volume than the old Ford can even dream about.
http://www.princessauto.com/mobile/product/productDetail.jsp?productID=8005213
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