Valve Stem Seals?

Sorry if this has been covered but I did a search and couldn't find all the answers I need... I'm going to change the valve stem seals on '98 GT.

So far, I've found out that I need to buy the OTC 7928 tool to do it with the heads on the car. Has anyone done it with a different tool that is more readily available?

Which valve stem seals do I need to buy? I found this write-up.

http://www.lincolnsonline.com/tech/00094.html

In it, he says he used a set of Fel-pro seals that he bought for $20. Does anyone have specs for these (or similar ones) or info on where they can be purchased? Or do I have to spend $80 at the Ford dealer?

Thanks in advance for your help!

I found the Fel-pro seals. In case anybody else is looking for them:

FEL-PRO Part # SS72891

Yeah, soon after I installed MAC long tubes. It had me stumped for a long time but checking out some of the other forums made it clear that its a big problem with the 4.6 - usually at 100k. The MACs really exasperate the problem.

I didn't notice it at first because I put on a catted h-pipe at the same time - the new cats absorbed most of the smoke. Now, I just hope I didn't fry the top end.