George, get something that you can wedge between the china rail and end of the intake, and pry with steady pressure. Keep the pressure on it and it may take a few seconds, but it'll pop loose. I use my gasket scraper because it's wide and flat and fairly stiff and won't ding the intake. Next time use Permatex Ultra Seal. It works much better than silicone but a lot easier to disassemble than Rightstuff. It's the wrongstuff. 
I am an end cork guy and I love Ultra Seal. However, as an old FE head that sees a lot of guys eliminating the end seals, I would warn you against Ultra Seal on the ends.
Ultra Seal is a little better than standard RTV, but the end rail surfaces on an FE are long and narrow and the bead is usually thick compared to a BBC or SBC. Granted, Edelbrock has closed them up a bit on the new manifolds, but still a lot tougher to seal correctly than other engines.
Right Stuff was the "right stuff", although you paid for the sealing with the adhesive, until people started finding porous/bubbles and seeping oil. Moreover, I think Right Stuff is the messiest, craziest crap ever made. Seems to get everywhere when I use it. TA-31 seems to be pretty darn good, but will also hold tight, maybe not quite as tight, but if using it in place of china rail seals you need it to grip. Just really need a better/longer blade to cut it.
I still like fitting the manifold for cork. I use 3M weatherstrip to glue them to the block and let them dry solid, then immediately before assembly I sparingly use Ultra Blue at the intake gasket/end seal junction and across the cork. It acts as a lube which allows the manifold to move and not push the end seal out. Then of course it hardens and helps seal. If you have the room, it's hard to beat. I have even made end seals out of thinner material to avoid having to count on a bead of sealant.
It'd be nice if someone made a good rubber seal with locating tabs on both sides of the wal, so that it would stay put, but nothing out there that I know of
I do this for a living and use Ultra Seal on every intake. I doubt if the tube of Ultra can tell if it's an FE or BB Chev. It seals very well even on long narrow wide gaps. Like with anything you use, it's all in the prep and how you install the intake. I use Super Weatherstrip on intake gaskets. It's good stuff too. I make temporary end seals out of different thickness rubber strips when I'm dyno testing intake manifolds, but for me, end seals are just a potential leak on a customer's engine. If I used them, I'd do exactly as you do.
Scott, appreciate the fact that you do this for a living, and you of course don't know me from Adam, but I was pulling wrenches professionally for Ford when Ultra series came out. Loved it and still love it compared to stinky RTV. In 1986 I opened my own shop and in 1995 we combined it with another family shop because I decided to join the USAF to fly. Through 1995 it fed us, put me through 2 college degrees has since then still pays for all my toys and tools, without touching any of my regular income, and all the time an FE guy. To be honest though, plenty of mice and rats paid the bills and much of the Ford work were fleets of FTs and FE pickups in the late 80s, all the more reason to not want to redo an intake
Now that I am done peeing on a fire hydrant, I am trying to help, if you don't want to agree, no need to and I am done talking, but from experience I do not think it's good advice for an FE, and I'd politely warn you not to do it on your upcoming build.
If this were a Chevy style rubber gasket, thinner gap and wider footprint, I'll give it to you in a heart beat. Ultra is a bit better than RTV, but not much and the china walls on an FE are different. Too much you push into a return, but you need a lot to fill a gap and the block wall is narrow. What generally happens with a non-adhesive type of gasket maker is that it lasts for a bit, and once oil crawls behind it, it lets go just like RTV.
Personally, I have never had an FE end seal leak. I have had some fight me until I was happy, often machining the intake, and even taping off the valley and using a coarse file to knock down a cork gasket to make it perfect, but pure sealer on an FE IMHO only works if you have an adhesive/gasket maker, and a tight gap.
