I don't run seals, if you remember chevy never put seals on their gides, just an O ring under the keepers and this on a street engine. The guides needed a little oil to keep them from wearing, and most did after a 100,000 miles, IE the little bit of blue smoke on cold startup on and old engines. Ford ran a little mushroom bonnet type seal, which is what i use on uncut heads. With the advent of bronze guides and alum heads they came with seals, because the guide were an oil impragnated bronze, but on strickly racing engines we cut back on the oil to the top of the engines, with roller lifters and rockers, and usually only a mist of oil on top, that why i don't use them. But as mentioned in an above post, if you are running a vacuum pump, they are probably a necessary idea. I've only ran an evac/header system, no experience with vacuum pumps.
JMO
Zip.