You could take the factory aluminum spacer and have it ported to match your TB opening... You really don't need to though, people run K8/KLs without the spacer all the time.
Ahh, you could grind the nub down on the TB or the space it would otherwise occupy on the manifold, was that picture from xtremethings.com?
The spacers shouldn't have any negative effect on your intake manifold, but you might need longer bolts to install them. IIRC, you can use the stock bolts, but you would only have a few mm of thread bite if you did so.
Try having your stock K8 throttlebody spacer bored out to 60+mm, and go from there!